technique

The benefit of thinking of green mixing in terms of the green mixing system is that its two layers unify the problems of mixing green as the way to realize the goals established by seeing and using green. In particular, the green mixing system foregrounds the problem of creating variety and contrast in your greens — by seeing the six basic dimensions of green, by planning suitable contrasts in color design, and by knowing how to recreate those contrasts in paint mixtures.

green mixing recipes

The advice to "mix a lot of greens" only provides you with a narrow part — the "get to green" part — of the green mixing system. To get the variety of greens you want, it can only recommend that you vary the proportions in your blue+yellow mixture.

Of course, it can also recommend that you use a different pair of blue and yellow paints each time you need a different green. But which pair, and why?

The answer to that question often determines the paints you choose for your palette, following one of three possible strategies. You can start with a palette that is quite large. You can design a palette that is specifically optimized for green mixing. Or you carefully choose a small number of blue and yellow paints that provide the optimal contrast in green mixtures. (See the examples by Lucy Willis and Charles LeClair.)

Whichever path you choose, the challenge now is to understand in greater detail how the paint mixing layer of the green mixing system is related to specific choices of blue, green and yellow paints.

This section summarizes the alternatives in terms of basic color categories; the next section drills down on the specific pigment choices within each category, and how they contribute to mixing variations.

Overview of Paint Choices. To begin, let's divide the color wheel into eight sections, and assume for now that the paints within each section produce similar green mixing results.

Three hues are available to mix greens: blue, green and yellow. These categories are each divided into "warm" and "cool" alternatives, to produce six hue categories that span more than half a visual hue circle.

The other half consists of two more sections: the warm colors and neutralizing colors used to warm, darken or neutralize a green mixture (diagram, below).

mixing sections of the color wheel

the dotted lines show the approximate location of the "balanced" hue within each section

First, what are the boundaries of "green mixing" paints at either end of the color range?

Orange yellow is the warmest yellow that will still mix a green with a blue or green blue paint. To judge by eye, the color must contain more yellow than orange. Because it is a saturated yellow orange, benzimida orange PO62 barely qualifies; cadmium orange (PO20), perinone orange (PO43) and pyrrole orange (PO73) do not.

However, the unsaturated yellow orange quinacridone gold (PO49) does qualify, as do raw sienna (PBr7), titanate gold ochre (PBr24) and some versions of gold ochre (natural iron oxide, PY43 or synthetic iron oxide, PY42). This alerts us that both chroma and hue affect the mixing behavior of paints.

At the other extreme, a violet blue such as ultramarine blue (PB29) is the warmest blue that will still mix a green with a middle or light yellow. Again, the color must contain more blue than violet, and chroma matters: indanthrone blue (PB60) is too dull, and ultramarine violet BS (PV15) is too violet to mix greens with a green yellow paint.

We can exclude all violet, red and orange paints because these colors cannot create a green mixture with a blue or yellow paint. They are useful only to warm, dull or darken an existing green paint or green mixture.

There are still many physical differences among paints in the same hue category — lightness, transparency, tinting strength, staining and pigment texture. But, as we've just seen, the difference between intense and dull paints has the greatest effect on the color mixtures. So within each of the eight hue categories, the pigments with the highest chroma for that hue, and the paints that are significantly duller or darker, are presented in separate columns.

The first lesson we draw from this table is that the scope of paint selections is very uneven across the hue and chroma categories. There is only one relatively saturated yellow green pigment, and only two relatively saturated blue green pigments, but a wide selection of both saturated and unsaturated yellows (diagram, below).

pigment locations within the color wheel

each dot represents a single watercolor pigment, with chroma indicated by distance from the achromatic center; convenience mixtures are omitted

Although there are more blue pigments than green, both hues are divided by the contrast between cobalt pigments, which are semitransparent, generally mid valued, rather coarsely textured and weakly tinting (and become semiopaque and whitish in the titanate variations), and the phthalocyanines, which are transparent, dark valued, very finely divided and strongly tinting.

Finally, there is an overall imbalance in relative chroma. The most saturated yellows are significantly more intense and lighter valued than nearly all blue or green paints, so they primarily act to increase chroma and lightness in any green mixture; the green and blue pigments tend to be both duller and darker valued, so they primarily act to decrease chroma and lightness.

As a general rule, both the blue and yellow or green and yellow paints have a comparable influence on the mixing line and on the transparency and handling attributes of the mixture. The yellow selection primarily determines the chroma of the mixture across the yellow green hues; the blue or green selection determines how dark the mixture will be across the green and blue green hues.

Five Green Mixtures. Now lets consider five different green pigment combinations, in terms of the reflectance curves of the separate paints and their mixture. The diagrams (right) show what happens "under the hood" in each case:

(1) green+yellow. The mixture of a green and yellow largely conserves a distinct peak of "green" reflectance, which supports a saturated green color; it also elevates the "red" reflectance while darkening any "blue" reflectance, which in combination increase the chroma and shift the hue sharply toward yellow. The resulting reflectance profile resembles the green of lawn grass or the springtime shoots of new foliage. In the gamut of artists' paints, this is perceptually the most luminous (intense and light valued) green, and is a warm green as well, resulting in a bright mixture.

(2) blue+green. The mixture of a blue and yellow paint produces a distinct peak of "green" reflectance, and an elevated "blue" reflectance with darkened "red" reflectance. These are the coldest greens and often among the darkest.

(3) blue+yellow. The mixture of a blue and yellow paint produces a subdued peak of "green" reflectance and a raised "red" reflectance, which shifts the hue toward dull yellow; these are excellent landscape greens because the mixture proportions of yellow to blue can be used to match the balance between orange and blue that defines the color of light.

(4) green+warm. The mixture of green with a near neutralizing warm ( orange red to yellow orange) paint — in the example, the red orange burnt sienna — produces a somewhat less prominent "red" plateau and lowered "blue" reflectance. As more neutralizing paint is added the green becomes warmer and eventually reaches the warm boundary between green and red, matching green foliage lit by the red light of the setting sun.

(5) green+neutralizer. The mixture of a green and its mixing complement, which can be anything from a red orange to violet, depending on the hue of the green and the depth of dark or gray desired. This produces a wavy or bumpy neutral profile, which to my eye gives grays mixed from green and magenta a unique and subtle luster, especially when the colors are mixed unevenly (wet in wet) or are contrasted in pigment texture.

You will see from the pigment identifiers that the five basic green mixtures can be made with just five paints. In fact, they are five of the six paints of the secondary palette, which is one of the smallest palettes that can mix every type of green.

Exploring Paint Recipes. The table lists too many paints to explore as separate mixtures (over 450 mixtures, in fact), but it lets us choose a single saturated and unsaturated pigment to represent each color category. My suggested choices are shown in bold and linked to each pigment's entry in the guide to watercolor pigments. Make other choices if you like, but start with one paint from each section.

The next step is to use these selected pigments to familiarize yourself with the basic green mixtures. This requires experience: you need to make the mixtures and look at the results for yourself. If you limit yourself to a selection of the twelve paints highlighted in the table (one from each category that is more saturated and one that is relatively dull, and excluding paints in the red to orange and violet to red categories), you have 4 orange yellow to green yellow and 8 yellow green to violet blue paints to explore. or 32 mixture combinations. This may seem a lot, but the mixing experience is essential to everything that follows.

reflectance profiles of five
common green mixtures

(1) bright: equal parts
green and yellow paint
(PG36+PY97)
(2) cool: equal parts
green and blue paint
(PB27+PG36)
(3) light: equal parts
blue and yellow paint
(PB27+PY97)
(4) warm: green paint with a
red or orange paint
(PG36+burnt sienna)
(5) dark & dull: green neutralized with its mixing complement (magenta or purple)
(PG36+PV19)

The infallible and most informative method is to make a mixing step scale for each of the 32 mixing combinations. In this way you see the mixtures as a range of greens rather than a single "color". More important, these step scales will serve you for years as a reliable color mixing reference; make them in a hardbound watercolor sketchbook.

The alternative is to premoisten a large mixing area (say, 4" square) on a sheet of watercolor paper, and mix the two paints wet in wet, and with added water, to get a full range of mixing ratios and wet in wet effects. This won't help you identify the paint proportions, but it gives an adequate overall impression of the "color harmony" created by the combined paints and can create a wider range of green mixtures than the controlled mixing step scale procedure.

Or you can make a "map of greens" on a single full sheet, as I did (above). My study put four color mixtures at the intersection of each yellow row and green/blue column, representing mixtures of yellow:green or yellow:blue paints in the proportions 6:1, 3:1, 1:1 and 1:3. This spread gives me a feel for the range of hues each mixture can produce. Whether the mixtures lean toward yellow or toward blue indicates the relative tinting strength of the two paints. For example, most of the mixtures under phthalocyanine blue are green or blue green, indicating it dominates almost every yellow pigment.

Whichever approach you use, don't try to complete the work at one sitting. Take your time and do two or three mixtures each day, for example as a "warm up" before starting work. In two weeks you'll be done.

As you work, you will identify attractive or evocative mixtures: use these mixtures in small sketch paintings. The real impact of colors only emerges when they are used in context. Get leafy bouquets from your flower shop, or treeful vistas from your local park, and crank out a dozen or so 4" x 6" sketches. This will draw your attention to specific green mixing problems and the results of different choices of paints.

Finally, make written notes of your observations. The best place to do this is alongside the test swatches themselves, or in a separate color mixing notebook. Comments such as "much duller, bluer color when dried" or "looked too gray in painting" will help you match mixtures more accurately.

Once you feel familiar with these two paint mixtures, you can explore the effect of mixing in a little neutralizing color — those red oranges, siennas, reds, crimsons, umbers and violets left out of the color mixing categorization. These are used as the adjusting color to make a green paint or mixture warmer or less intense.

Among the paints most often used in this role are burnt sienna (PBr7), venetian (indian) red (PR101), burnt umber (PBr7), cadmium orange (PO20), cadmium red (PR108), perylene maroon (PR179), quinacridone rose (PV19) and dioxazine violet (PV23). There are many other paint choices across this color range, provided you avoid alizarin crimson.

These paints are all mixing complements of various shades of blue or green, so they pull the green toward gray (desaturate it), lighten or darken it (depending on the value of the two paints), and sometimes add pigment texture or granulation. In the section on natural greens (below), I show that most natural greens are rather dull, so you will need to learn how to use the dull green+warm or green+complement mixtures in order to paint landscapes effectively.

pigment choices

An important benefit of these color mixing exercises is that you learn the mixing attributes of specific pigments (paints) — not as "colors" but as substances with attributes such as tinting strength, transparency, staining, granulation and diffusion.

My experience suggests the following observations, which I pass on to bring some issues to your attention and guide your selection of pigments to explore. These comments cannot in any way substitute for your own experience with the paints, but they suggest what you should look for.

Yellows. There is a large number of yellow pigments available in watercolors, but they all can be classified into four groups:

(1) The cadmium yellows (PY35/37) are always among the most saturated pigments in any yellow or yellow orange hue. They tend to be expensive and semiopaque, but they are hard to beat for color purity, high saturation, high tinting strength, ease of handling and permanence. This means specifically that they hold their color even in tints, and those tints are very lightfast. (Note, however, that some brands may gray or darken under certain conditions, as documented in the guide to watercolor pigments.) Nearly every artist's palette I have seen includes at least one cadmium yellow paint.

A major difficulty with cadmiums is their high specific gravity (they are essentially metal pigments, about as heavy as iron oxides) and their aggressive diffusion in brands such as M. Graham, Rembrandt or DaVinci. Especially in mixtures with the phthalocyanines, the cadmiums can settle quickly to the bottom of the mixture puddle, causing the mixture to look like it contains less cadmium than it actually does. If the mixture is painted as a juicy brushstroke, the cadmium can settle first to the paper, in effect forming a base layer that is "glazed over" by the other pigment.

In either case, the true color does not appear until the paint has completely dried. If color control is essential, there are two solutions: (1) make test paintouts on a scrap piece of paper, and let dry, to judge the mixture; (2) paint the cadmium yellow first, as a foundation layer, then glaze the green or blue paint over it. Because the phthalo colors (green and blue) are the most transparent watercolor pigments available, this method works very well.

Another problem is that you must have a delicate but confident touch. Especially when used in concentrated mixtures, the cadmiums must be laid down without fussing. Rebrushing or retouching a passage of cadmium paint while it is still wet can quickly dull the dried color, producing an effect like scuffed velvet. When applied wet in wet, the cadmiums produce a lovely, powdery mist of color, and their weight, active diffusion and opacity usually causes them to separate slightly from other pigments if applied in juicy brushstrokes or wet in wet (especially in backruns), producing interesting and expressive pigment effects.

All things equal, the bright green mixtures created by cadmium lemon (or cadmium yellow pale) offset any difficulties. For that reason it's much more common for artists to use a greenish rather than a reddish cadmium in their palettes.

If highly saturated color is what you're after, be aware that, regardless of pigment, the most saturated yellows are middle rather than lemon hues. For example, the chroma of a good middle cadmium yellow is at or above 97, while the average chroma of a cadmium lemon is only 91. (The same difference appears in the synthetic organic yellows, for example between hansa yellow light, with a chroma of 90, and hansa yellow, with a chroma of 99 or 100.) So, even though the middle yellow contains "more red" or is "warmer" (in the wacky world of the "split primary" color theory), it can actually mix greens as saturated as a cadmium lemon!

(2) Weaving through the span of cadmium hues is a group of saturated synthetic organic yellows, including the arylide (hansa) and benzimidazolone paints, plus a few exotics such as anthrapyramidine yellow (PY108), isoindolinone yellow (PY110) and quinophthalone yellow (PY138). In terms of the range of mixed greens they create, these pigments are almost indistinguishable from the cadmiums, and they typically cost less.

Compared to the cadmiums, there are several differences in their mixing behavior: they are more transparent and typically have a lower tinting strength and are more sensitive to backruns; they tend to lose color more in tints. Most will not separate if mixed with the phthalocyanines and applied in juicy wash, so you have better control of the finished hue as you mix it.

In my evaluations, the most saturated yellow available in watercolors is the arylide pigment hansa yellow (PY97), which is also lightfast and semitransparent. The benzimidazolone yellows (PY151, PY154 and PY175) are also worth looking at, although their lighter value causes them to have a slightly lower chroma.

(3) The third major group is the metal yellows, which include green gold (copper azomethine yellow, PY117 or PY129), nickel azomethine yellow (PG10 or PY150), and nickel dioxine yellow (PY153). The azomethines are the most transparent yellow pigments available, have good tinting strength (unless the watercolor brand has reduced the pigment load), and have a slightly unsaturated (brownish or greenish) color and a slightly granular texture in masstone. All the paints show a strong color shift (toward green) from masstone to tints.

In terms of its color, transparency and hue shifts, the recently expired quinacridone gold (PO49) can also be included in this group. Like hansa yellow, it was very often used in convenience green paints, and produces mellow, transparent and pleasingly dark yellow green mixtures.

These paints are exceptionally good in landscape work, especially when mixed with transparent blues or greens such as the phthalocyanines or iron blue (PB27). As they tend to be on the warm side of the yellow range (which causes them to make less saturated mixtures with green or blue pigments), their unsaturated color isn't objectionable. It turns out to be a benefit: these yellows mix the most natural, consistent and muted range of yellow greens you can get, and the lightfastness of the mixtures is very good. The transparency offsets the lack of saturation: the mixed greens are duller, but also cleaner looking and easier to handle.

(4) The last group of yellow pigments is the diverse earth yellows, including yellow ochre (PY43), raw sienna (PBr7), raw umber (PBr7) and gold ochre or transparent yellow oxide (PY42).

The earth pigments can mix very natural greens, but some (gold ochre and yellow ochre) tend to make opaque or dull mixtures and, like the cadmiums, will separate if used in juicy applications with the phthalocyanines. As with the cadmiums, the cure is to glaze the darker paint over the earth yellow applied as a foundation, or to mix earth greens with similarly textured cobalt green or cobalt cerulean paints. (These mixtures must be used in diluted, juicy washes, as they will appear unreflective in masstone, and will muddy if fussed with after they are applied.)

I've excluded from consideration the opaque and whitish titanium metal complex yellows — nickel titanate yellow (PY53), chrome titanate yellow (PBr24) and Winsor & Newton's turner's yellow [hue] (PY216) — pigments originally developed for applications such as aluminum siding and ceramics. These titanium based paints are less satisfactory because they add a whitened luster to any green mixture that does not much resemble vegetable greens, though they might be apt to render desert adapted plants such as yucca, palm or aloe.

The earth paints are cheap and reliable, but I find that the combination of unsaturated color and opaque texture is difficult to manage: the finished color often looks flat and heavy. Convenience greens made with phthalocyanines and iron oxides suffer the same problems and should be left to "student" grades of paint.

Greens. In terms of saturated, strongly tinting and completely lightfast pigments, the greens, blues and violets are the impoverished sections of the color wheel. Not only are the available pigments in these hues rather unsaturated — there are relatively few of them. They form three distinct groups:

(1) The major class of green pigments is indisputably the phthalocyanines, which come in two hues: phthalocyanine green BS (blue shade, PG7) and phthalocyanine green YS (yellow shade, PG36). Although relatively dark valued (the blue shade is darker than the yellow), these are strongly tinting, strongly staining, moderately saturated and very lightfast pigments. Almost every artist's palette I know of includes one of the phthalo greens or a convenience mixture made from them.

The most saturated and darkest green mixtures possible combine a saturated yellow with a phthalocyanine green paint. The phthalocyanines provide the maximum color saturation and maximum value range possible in a green mixture. The phthalocyanines are also transparent and have a perfectly liquid texture. They define the chroma and darkness limits of what you can do in green mixtures.

Main concerns with the phthalos: a strong tendency to stain and high tinting strength. The staining is a plus if you use the phthalos as a foundation that you glaze over with a color you want to lift away. For example, if you glaze over a phthalo paint with a cadmium yellow, you can lift away the cadmium (by wetting and blotting) to reveal areas of green within the color field. (Jim Kosvanec's claim that the phthalos will "stain" the opaque cadmiums and give you "mud" depends on how the paints are used.)

The high tinting strength simply means — use with caution! It's very easy to overwhelm a mixture with what seems like a tiny amount of phthalo paint, especially when the phthalo is only moderately diluted. My rule is, choose the amount you think is correct to add to a mixture, then add one third of that to start.

Because of their very fine particle size and low specific gravity, the phthalos easily separate from heavy (cobalt blues, earth yellows) or opaque (cadmium yellow, bismuth yellow) pigments in juicy mixtures. The best remedy, as described above, is to put down the yellow color first, let it dry completely, then glaze the green or blue phthalocyanine on top. But the pigment separation can produce interesting and attractive patterns and variations in the color area.

Besides the steroid phthalos, there is a handful of granulating, rather opaque and unsaturated cobalt and chromium pigments.

(2) There are two chromium greens. Viridian (hydrous chromium sesquioxide, PG18) is a traditional green the exact same hue as phthalo green BS — but usually granulating, nonstaining, and slightly less saturated and lighter valued. It is much weaker in mixtures, even with iron oxide yellows. Some artists prefer it because it mixes more natural (slightly dull) greens, and is much easier to lift or correct if needed. It works especially well with cadmium paints of any hue; it makes a lovely iridescent gray with most cadmium reds.

The sleeper is chromium oxide green (anhydrous chromium sesquioxide, PG17), a very dull yellowish green close to the hue of many sap greens (it is commonly used in camouflage paints). Unlike mixed sap greens, however, it is very opaque. In very diluted mixtures it creates a hazy, delicate texture and is quite effective at creating a wide range of natural, warm, muted greens when added in small amounts to any yellow pigment. Its opacity also lends substance to green passages that should appear heavy. If you have struggled to get natural looking landscape greens using the phthalocyanines, I urge you to give chromium oxide green a try (or viridian, for that matter). Just remember: the semitransparent viridian can be applied in fairly heavy concentrations, but the very opaque chromium oxide green works best in diluted mixtures or added to mixtures in small amounts.

(3) Finally, the green cobalts. Cobalt green comes in a few different flavors (PG19, PG26 and PG50): all are semiopaque, unsaturated, granulating, weak in mixtures, and very sedimentary. (Cobalt teal blue, PG50, because of its light value, mixes surprisingly bright yellow greens.) If you mix these with cadmium or earth pigments, keep the mixture well diluted — otherwise you really will get a dull color.

The cobalts work best with the synthetic organic or metal yellows, but tend to sludge over these pigments in juicy applications, shifting the mixed hue toward a green. Probably the most acceptable are the cobalt titanium greens (PG50), which also come in a blue and yellow shade. But their whitish color limits the value range of the mixed hues, and they separate from the yellows as well. I find them hard to work with.

You may also run across paints labeled terre verte or green earth. If these really are earth pigments, rather than hue substitutes made from chromium or cobalt pigments, they are more often used in portrait than in landscape work, as a foundation color to render facial planes that are shadowed or obliquely lit. They are usually very weakly tinting, dull, transparent, and moderately light valued.

Blues. The blue pigments can also be classified into three groups:

(1) As with the greens, the major pigment class of blue pigments is the phthalocyanines — which come in a broader range of shades, from phthalo turquoise (PB16), phthalo cyan (PB17), phthalo blue GS (green shade, PB15:3), and phthalo blue RS (red shade, PB15:1). (Phthalos without the red/green distinction tend toward the red end of the color range: see the color chart displayed under phthalo blue.) Because of its dark value, tinting strength, transparency and staining, iron (prussian) blue (PB27) should be included in this group as well.

All the previous comments under the phthalo greens apply to these blues as well. Although relatively dark valued, these are strongly tinting, strongly staining, and moderately unsaturated colors. The pigments have a very low specific gravity and extremely small particle size, so they are unusually susceptible to backruns and diffusion wet in wet. The chroma of these paints increases as they are diluted up to a middle value, producing lovely bright tints that are unusually good as sky colors. Iron blue in particular mixes evocative dark greens, especially in landscapes, and is not as saturated as the phthalos and therefore mixes more subdued shadow purples. Its one drawback is that it is occasionally less lightfast in tints. The choice between a phthalo or iron blue is primarily one of mood and delicacy of color, especially if the same blue is used for landscape greens and skies. All are valuable to explore and to have on your palette.

(2) Overlapping the hue range of the phthalocyanines is the second category of blues, the many cobalt pigments. Cobalts start out fairly saturated in the blue violet or reddish blue hues (PB73 and PB28), but decline in saturation as the hue shifts toward turquoise because of increasing amounts of chromium. (See the color chart under cerulean blue PB36, and the hue and saturation positions of the cobalts in the artist's color wheel.)

In the "color theory" explanation of the "split primary" palette, a greenish blue pigment should mix (with yellow) more saturated greens than a reddish blue. But in the cobalts this simplistic rule breaks down. The decreasing saturation in the greener cobalts counteracts the increase in the green hue; the different cerulean and turquoise cobalts mix very similar, unsaturated, granulating greens.

Cobalt teal blue (PG50), at the boundary between green and blue, is the exception. It has the same hue as cobalt turquoise but is somewhat more saturated because of the whitening effect of titanium. It produces somewhat more saturated green mixtures than the other cobalts, although it can't achieve a very dark value. Like the titanium yellows, it tends to add a whitened luster to mixed colors. It is however very effective as a foundation wash, glazed over by darker deep blue paints, to give skies a glowing middle blue hue.

All the cobalts are granulating and semiopaque, which opens up interesting artistic effects but also makes the paints more troublesome to mix and apply without the colors separating on the page.

(3) The last group of blue pigments is a handful of unique pigments: manganese blue (PB33, ultramarine blue (PB29) and indanthrone blue (PB60).

You're unlikely to use the first of these blues. Manganese blue is difficult to obtain, highly polluting to manufacture, strongly granulating, and usually packaged with a gummy vehicle. (Personally, I love the stuff for its color and texture in landscape washes and portraits, but it has never been very popular.)

Ultramarine and indanthrone blue are quite dark, relatively saturated red blues, and they are valuable for mixing dark greens very close to gray — pine trees seen in the distance, or eucalyptus trees in a haze. Neither one makes a very good dark pigment: ultramarine blue is too saturated, and indanthrone blue tends to have a whitish sheen. They will mix to green with any yellow pigment up to benzimidazolone orange (PO62). But they are not essential: nickel azo yellow and phthalo blue, with a touch of quinacridone rose, will mix equally effective transparent, dark greens.

green mixing problems

There are several specific problems with mixing greens that need to be discussed separately from the mixing system and the "colors" that make it work.

Green Value & Chroma. Context is the main reason why a green mixture recipe by itself is not going to get you to a satisfactory green or confident mastery of green mixtures. Confusion often arises from the idea that "color" exists separate from context.

Asking the question "what is a good green mixture?" is like asking "what is a good green chair?" After all, you want the green chair to fit in with everything else in your room, but usually any random green chair is going to clash with other colors in the room.

Friends recommend this or that green chair, and after trying several out you go, "aha, here is the green chair I've been looking for!" and the room you put it in looks great. But there are many rooms in your house, so now you go to a different room — different color scheme, more light, different side of the house — and the same chair looks wrong again. Darn it! You have to start looking for green chairs all over again.

In this anecdote the green chairs are different paint mixture recipes for a "good green," and the different rooms are different landscapes, different botanicals, different painting contexts in which the green mixture appears.

The basic problem is that green must represents three different visual facts at the same time. It represents a value or lightness in your value scheme, determined by the amount of light shining on it; it represents a surface color that depends on the concentration of chlorophyll in a specific type of plant (an oak green is different from a maple green; grass green is different from cactus green, etc.); and it represents a mixture of light and surface color that reveals the brightness and hue of the ambient light. Just "finding a good green mixture" means you must paint all these visual facts the same way.

The solution for the value scheme problem is to examine the sequence of greens from lightest valued to darkest, and paint them in order from one extreme to the other, systematically increasing or decreasing the concentration of green paint in water. Do this with any reasonably dark, middle green paint or mixture, in the same way you would lay down the value scheme using a black paint: dilute the paint for lighter values, and below its masstone value add black or a complement to darken it further.

Once you get the value relationships approximately right, look next at the hue. Then render hue by glazing over the foundation color with a transparent yellow or blue paint. This will darken the color somewhat — more for the blue than for the yellow, which will slightly increase the value range.

Another approach is to use a bright or "neon" green, such as Daniel Smith's phthalo yellow green or Rowney's vivid green, and paint in all greens with that paint to start, then let the greens completely dry. This puts the green far into the light values and yellow hue bias. Most of the greens will be screamingly wrong no matter what it is you are painting. But they will be so wrong that you will easily see what is wrong — they need to be dulled with quin gold, or burnt sienna, or quin magenta, or shifted toward blue with dioxazine purple, or phthalo blue, or phthalo blue green — and this process helps you understand how to see and adjust hue differences.

Adjusting hue and value usually dulls the green to approximately the right chroma, but if the green is still to intense, then glazing over with a diluted mixture of the green's mixing complement will get it right.

Foliage Greens. Once you have a basic green painting approach, the next hurdle is overcoming the "color idea" that prevents you from accurately seeing the foliage green you want to paint. To break out of that conceptual box, it helps to locate foliage greens in the CIELAB color space, the same space where we've mapped the mixing lines.

The figure shows the visual color wheel with the hues ranging from 100% saturation or 100% brightness along the rim to 0% saturation or brightness (black) at the center. The background color tiles decline in brightness and saturation in 20% steps.

Superimposed on the wheel are the approximate hue and saturation positions for the leaves of a variety of common plants and trees — dead and alive — as sampled from color digital photos taken in early afternoon light (in California, USA during May).

foliage greens on the visual color wheel

foliage greens measured from photographic samples taken at the same viewing angle under noon sunlight

Look first at the overall distribution of greens. The saturation of natural greens is much less than the maximum possible: about 90% between the lemon yellow and yellow green color points, and declining steadily to less than 50% as the greens approach blue green.

With the exception of rose leaves, which are fairly saturated, dark bluish greens — most foliage on the blue side of the distribution (pine, yucca or eucalyptus) — are very sharply unsaturated. Interestingly, the value of these bluish green hues varies quite a lot, from the light valued eucalyptus to the very dark valued pine. I don't know what general the rule may be across botanical species, but it seems that bluish green foliage takes on an especially wide range of values.

At the other extreme, the yellowish greens are generally more saturated and typically have middle to light values. These include the greens of most deciduous trees, flowering plants, lawns and, at the extreme, those young shoots that are so brilliant and distinctive in early spring.

An easy way to remember the location of natural greens is that they mostly fall along a line drawn parallel to the "primary" yellow (vertical) spoke of the color wheel (roughly from the tiles for "japanese box hedge" to "eucalyptus" in the figure), but shifted halfway toward color point 12 (permanent green light). The result is that from yellow green to blue green, greens darken and lose saturation. In florals or landscapes, the blue greens will typically appear darker and duller than the yellow greens.

The green and blue versions of phthalocyanine green (shown in the diagram) are too saturated. There are very few natural greens the color of either phthalo pigment by itself. We cannot readily use these colors without modifying them, which throws us back on the difficult task of hitting the natural colors through a mixture.

This distribution of greens also suggests why it is so hard to hit a natural green by a mixing yellow with a green or blue pigment: the yellow to green/blue mixing lines (shown in the previous diagram) run horizontally, while the spread of natural greens runs vertically. It's like pitching horseshoes: it's easy to undershoot (too yellow) or overshoot (too green) the goal.

This is why paints such as sap green are so popular, even among artists who otherwise only use single pigment paints. It lies in the center of the natural green distribution — no worries about hitting the color exactly. Added yellow takes the color toward new deciduous leaves, added blue violet takes it toward pine or olive, added phthalo green takes it toward geranium. It radiates natural greens in all directions.

Many artists underutilize the warm mixing potential of sap green. Combined with quinacridone rose, burnt sienna or benzimidazolone orange (PO62), sap green mixes lovely muted browns, tans and olive greens, the color of parched, dried or dead leaves. It can generate both the living and dead colors of plants and trees.

Green Bias and Daylight. Understanding the basic surface color of vegetable greens is a good start, but these greens mix subtractively with the color of the light falling on them, and they appear to shift in hue — from blue toward yellow — as the intensity of incident illumination increases. So you need to understand how greens behave as the light around them changes.

The common types of landscape illumination are the phases of daylight, which include changes in total light from noon to darkness, and the contrast between lighted and shadowed surfaces. The two standard illuminants used to study these effects are: (1) daylight at one hour before sunset, which produces a deep yellow or orange light (CIE illuminant A); and (2) daylight at noon, which produces a bluish and intensely bright light (CIE illuminant D65). Note that both the intensity of light and its color are in play.

What is the mixture produced by these illuminants and the green surface color? To answer that, we need to define the green. The spectral reflectance curves for typical foliage greens tend to match one of two patterns (right): a gradually increasing reflectance from "blue" to "red", which resembles the reflectance profile of a raw sienna or green gold; or a modest bump of "green" reflectance and a sharp increase in "red" reflectance into the infrared, which resembles the reflectance of green grass or camouflage paint (chromium oxide green, PG17).

What happens to these reflectance profiles under the two contrasting colors of illumination?

green bias and color of illumination

the product of two illuminants on the same colored surface; adapted from Jeff Beall, Adam Doppelt & John Hughes © 1995 Brown University

In both cases the change in light color produces a strong shift in green color. In the first example the shift is from a middle green or forest green to a midvalued yellow green or olive green. In the second example the shift carries the color all the way from green into yellow (brown)!

This sensitivity of hue to illuminant color is related to the general problem of metamerism, and the fact that metamers (or light induced color changes) are more likely in the area of yellow greens to deep yellows. This is why Monet chose to paint haystacks instead of hedgerows: the ochre hay showed changes in the color of light most clearly.

The twist here is that the chroma of all the other colors in the painting state the light to the eye, and if they all don't harmonize with the green to say "cloudy day" or "afternoon light", then the green will pop and squirm even though the color match between your green paint and the green plant is accurate, and regardless of whether the green is light or dark, yellow or blue, intense or dull. Green must fit the light, or green becomes obtrusive.

green bias and color of illumination

This diagram summarizes the contrast in hue shifts with changes in daylight phase. In general, solar light causes hue changes from yellow to green; sky light (which illuminates shadows) shifts the same hue of green into a darker value with loss of saturation.

Green Mixing Curves. As you look over your many exploratory green mixtures, you've probably noticed many unexpected, disappointing or confusing results. You may feel as if the paints somehow pitched you a curve ball. Turns out you'd be right.

These problems are the reason for the many sap greens, hooker's greens, permanent greens, emerald greens, grass greens, olive greens, brilliant greens and other premixed greens available in watercolors. These paints are all convenience mixtures of a phthalocyanine and yellow pigment. They provide a reliable, readymixed green as the starting point for consistent and effective green mixtures.

mixing lines for greens are actually ... mixing curves

A very confusing fact about greens is that the mixtures are more intense (saturated) than we expect. Using spectrophotometric measurements of actual paint mixtures, I've plotted on the CIELAB a*b* plane the mixing lines between two yellows (the unsaturated deep yellow quinacridone gold, and the saturated light yellow hansa yellow) to the major phthalo greens and blues, and the saturated red blue, ultramarine blue. These mixing lines bracket the most saturated green mixtures possible, and trace a typical range of unsaturated green mixtures.

As you see, the mixing lines on the green side of the color wheel are curved, not straight. (This finding also came up when we tested the color wheel using "primary" color mixtures.) The mixing lines for quinacridone rose, which are close to straight, are included for comparison.

Greens are the "curve ball" in color mixing. But these curved color paths are only the surface symptoms of other subtle and complex problems that turn up when making green mixtures:

• Rapid color change. As yellows are mixed with a blue or green paint, they quickly darken and shift clockwise on the color wheel. As a result, the mixture seems to shift suddenly toward a middle green. As blues are mixed with a yellow paint, the darker value of the blue makes it dominate the mixture, pulling the color toward a blue green. Then, when the mixed color has dried, it becomes significantly lighter valued and less intense. (The overall drying shift can be as large as 30% to 50% of the wet mixture's lightness, chroma and hue.) So the mixture on the palette is always very different from the dried color on the paper. These problems are the primary reason why green mixtures seem uncontrollable, and why intense, "yellow" greens or rich dark greens are so difficult to mix accurately. The remedy is to slow down and treat mixed greens with more attention: you will learn to compensate for these problems more quickly.

• "Yellow" greens. Yellow turns into an apparent green — usually a light valued, olive or golden green — while the hue of the color is still actually yellow (as shown by the green boundary in the figure). In fact, an unsaturated green color is easily made by mixing a lemon or middle yellow with a touch of black pigment, which shifts the color straight toward the center of the wheel. (Dull, dark chromium oxide green works on yellows in a similar way, and produces lively but delicate greenish yellows and leaf greens.) These green golds are within the unsaturated color zone for yellow, but seem to be on the green side of the color wheel. This again makes accurate mixing difficult: we may try to get these colors by mixing yellow with a touch of green, but the result will be too green.

• Desaturating warm shift. Many artists use a dull scarlet or orange paint, such as burnt sienna (PBr7), to desaturate their green mixtures (shift them closer to gray). But these colors actually shift the green hue back toward yellow as much as or more than they shift it toward the neutral center of the wheel, resulting in a yellowish green color. The best paints for desaturating green mixtures straight toward gray are much bluer, such as dioxazine violet (PV23) for a yellow green, and quinacridone carmine (PR N/A) for a blue green. Of course, if a warm shift is the effect you want, then a transparent red iron oxide or burnt sienna is ideal.

• Blues for blue green. Even though phthalo green BS is a very bluish green, it's often a poor choice for mixing blue greens. The reason: it's too saturated. As with the dull greens tucked under saturated yellow, there are dull blue greens hidden under saturated blue green. You can't reach these evocative blue greens by mixing phthalo green and a yellow paint. Use the phthalo greens to mix yellow greens: blue greens should either be mixed with a yellow and blue paint — phthalo cyan, phthalo blue, cerulean blue, or ultramarine blue — or by dulling phthalo green BS with one of its many scarlet or red mixing complements.

• Phthalos light and dark. It's common to think of the phthalo greens as differing in hue — yellow and blue shade. The key difference, however, is in value. Mixed with light yellow, the two shades of phthalo green produce very similar trajectories across the color wheel; their hue differences don't matter much in the saturation of their mixtures. But phthalo green YS (PG36) creates saturated mixtures in a higher key (lighter values), while phthalo green BS (PG7) produces darker values and a greater value range overall. Use phthalo green YS if you must mix light valued, saturated greens (spring shoots, banana leaves, parrots), but try phthalo green BS for saturated darks (dark floral greens, rose leaves). A similar contrast applies in the choice between phthalo cyan (PB17) and phthalo blue GS (PB15:3).

What about the convenience greens? The CIELAB location of permanent green light and sap green (see diagram above) shows that they are roughly centered within the fan of green mixing lines emanating from a bright or dull yellow. The benefit of these two convenience greens is that they reliably locate a specific hue, value and saturation of yellow green at a point where most yellow mixtures produce very similar colors. (Hooker's green and permanent green deep provide similar locations at a bluer hue point.)

Besides saving us the trouble of mixing the approximate yellow green we want, these convenience mixtures also make varying the green hues much simpler: we simply mix the convenience green with any other paint. Surprising as it sounds, olive green, sap green, permanent green or hooker's green are all located where added yellow, orange, red, magenta, violet, blue, blue green, earth colors, black or white will produce an interesting and distinctive new green shade. Expressive landscape or botanical painting can be reduced to liberal use of sap green, tweaked by random touches of whatever other color suits your fancy, and complemented with specific mixtures of yellow and blue to provide other green accents.

Finally, it's worth knowing that the mixing color wheel attempts to fix this curvy business with mixed greens by scrunching the greens and blues closer together on one side of the wheel, as shown in the diagram (compare the visual and mixing wheels on this page).

the mixing color wheel "fix" for curved mixing lines

But this doesn't really solve the problem of curvy mixing lines, since now the mixing lines in other parts of the wheel are wrong. Mixtures of rose and yellow are much more saturated than a straight mixing line on the mixing color wheel implies, and mixtures of rose and blue are less saturated than the straight line implies. We'd need outward or inward bowing mixing lines to compensate. And the green mixing lines are still misleading — they don't accurately represent the saturation of mixed colors (compare to the figure above) — and the perceptual relationships among colors are entirely lost. With this wheel, we've also lost the visual complementary relationships among the colors.

Every color wheel distorts the color space in some way. But it's simply not possible to create a simple mixing wheel that gets accurate, straight mixing lines among all colors and still preserves complementary color relationships and saturation information. The visual color wheel does force you to work with curvy mixing lines — but this discipline leads to a much deeper understanding of how paint mixtures actually create new colors.

generic foliage reflectance profiles

Matching Greens. The low saturation of many natural greens helps to explain why artists are typically content to put most of the saturation costs in their palettes on the green side of the color wheel. Many artists omit a green paint from their palette entirely, mixing all their greens from whatever blues and yellows they normally include on their palette.

If you use a green, you probably will not need anything more than phthalocyanine green BS or phthalocyanine green YS for a green pigment, since these are darker and more saturated than most natural greens.

Once you have determined the colors you'll use, create a mixing step scale between the most saturated and greenest (lemon) yellow and the greenest blue (or green) on your palette: this defines the most saturated greens it's possible for you to mix.

It's worthwhile to do these mixing step scales for all combinations of yellows (including earths), greens and blues in your working palette. Paint these "green scales" on two sides of a piece of 600 GSM watercolor paper (or watercolor board) cut to a convenient size to use in the studio or carry in the field. These scales are useful to identify the best mixing approximation for any natural green hue: once you find a close match, you will know which two paints (in what proportions) give you the mixture. (These cards take a lot of mixing effort: I suggest you make two or three at a sitting, so you'll have a spare in case the other gets lost or damaged.)