hue purity of watercolor paints

This page publishes my calculations of the hue purity of generic watercolor paint pigments, as explained in the section on hue purity and optimal colors.

This page includes CIECAM coordinates, averaged across all paint brands, for over 170 pigments, including most of those discussed in the guide to watercolor pigments.

The maximum hue purity or MacAdam limit was calculated from the CIE 1964 10° standard observer (Stiles & Burch colormatching functions) under an equal energy (EE) illuminant.

Unclassified mineral pigments, marketed by Daniel Smith as Primatek™ paints, have been included to suggest the range of moderately chromatic natural minerals — that is, the range of inorganic surface colors typical of the environment to which human vision is adapted.

Each row, in order of increasing hue purity, lists:

COLOR INDEX — generic C.I. name of the pigment (this is missing for convenience mixtures and unclassified mineral pigments)
PIGMENT NAME — common pigment name or marketing name
J, aC, bC — pigment location in the CIECAM color appearance space
C — CIECAM pigment chroma, defined as (aC2+bC2)0.5
Hue Angle — CIECAM hue angle, defined as ARCTAN(bC/aC)
Hue Purity — CIECAM hue purity, the ratio between the pigment chroma and the chroma of the optimal color of matching lightness and hue angle
aHP, bHP — ab coordinates for pigment hue purity, scaled so that maximum possible hue purity equals 1.0

All the pigments with the highest hue purity, above 70%, are confined to the orange to red hue span (pyrrole orange PO73, pyrrole scarlet PR255 or pyrrole red PR254), with the sole exception of ultramarine blue (PB29).

The scatterplot below suggests both that optimal colors can be used to further refine the CIECAM chroma estimator, and that optimal colors (physically possible colors) may define an ecologically valid stimulus limit in the adaptation of human vision (and perhaps all terrestrial animal vision).

COLOR INDEXPIGMENT NAMEJCaCbCHue AngleHue PurityaHPbHP
.sodalite153-301820.04-0.040.00
PBr6iron oxide black17754380.070.050.04
.hematite216-16950.08-0.010.08
.kyanite4110-1021700.09-0.090.02
.vivianite3512-981400.11-0.080.07
.jadeite179-761410.11-0.090.07
PBr33zinc iron chromite brown2514128330.120.100.06
.bloodstone221068550.120.070.10
PBk31perylene green2111-881330.13-0.090.09
..indigo1912-1-122670.13-0.01-0.13
.purpurite2013133130.130.130.03
.hematite violet26141010470.150.100.11
.piemontite20161211400.160.120.11
.zoisite2215-9121280.17-0.100.13
.cote d'azur violet37221417500.190.120.14
.tiger's eye burnt23191215510.200.130.16
.green fuchsite6029-25151490.21-0.180.11
PBr7burnt umber28251816420.210.160.14
PG17chromium oxide green3524-18161390.21-0.160.14
PG8hooker's green2623-19141440.22-0.180.13
.bauxite24211516470.220.150.16
.apatite2016-14-82080.23-0.20-0.11
PBr7raw umber34231220590.240.120.21
PR101mars brown36292021470.240.170.18
PR101mars violet25262510210.240.230.09
.red fuchsite41312717320.240.210.13
PR101lunar red25302615310.250.210.13
.malachite5033-22241330.25-0.170.18
.hematite burnt scarlet25322619360.260.210.15
.lazurite2625-16-192300.27-0.17-0.21
PG26cobalt green dark3327-2701800.28-0.280.00
.azurite2625-20-142150.28-0.23-0.16
.serpentine2723-8221100.28-0.100.27
.yavapaiite29271424600.300.150.26
PB27+PY35prussian green2527-25-81980.31-0.29-0.09
PR233pinkcolor42383416250.310.280.13
PBr41disazo condensation brown29393321320.310.260.17
PBr25benzimidazolone brown31403421320.320.270.17
..hooker's green3337-30211440.32-0.260.19
.pipestone33433524350.320.270.19
.sedona31403027420.330.240.22
PV23dioxazine purple203115-272990.340.16-0.29
..sap green3334-20281260.34-0.200.27
PR101indian red33413718260.340.310.15
PR101venetian red31423719280.340.300.16
.tiger's eye2315314770.340.080.34
PR171benzimidazolone maroon2637369140.350.340.09
PR101light red33443824320.350.290.18
PBr11magnesium ferrite brown40483632420.350.260.23
PB60indanthrone blue18320-322710.350.00-0.35
..olive green3331-531990.36-0.060.35
PBr7burnt sienna37484027350.360.300.21
PG50cobalt titanate green YS4246-41201540.36-0.330.16
PY53nickel titanate yellow8546-246920.36-0.010.36
..naples yellow75451941650.370.160.34
PG19cobalt green5040-39-71900.39-0.38-0.07
PY119mars yellow43503438480.390.260.29
PBr7raw sienna55482342610.390.190.34
PBr24titanate gold ochre68532448640.390.170.35
PY42yellow ochre58502245640.400.170.36
PV16manganese violet314439-213310.400.35-0.19
.green turquoise3042-40111640.41-0.400.11
PY42mars yellow53502444610.410.200.36
.blue turquoise3643-42-91930.43-0.42-0.09
PY42gold ochre50583745510.440.280.34
PB27prussian blue1940-17-362450.45-0.19-0.40
PV15ultramarine violet (red)364221-372990.450.22-0.39
PG50cobalt green [BS]5048-4801800.45-0.450.00
PY129green gold5349449860.460.040.46
PG10nickel azomethine green5856-855980.47-0.070.46
PR88thioindigo violet295050-23580.470.47-0.02
PR175benzimidazolone scarlet31565026270.470.420.21
PO49quinacridone gold52603350560.470.260.39
PV14cobalt violet deep464733-323160.470.34-0.33
PB27antwerp blue3548-29-382330.47-0.28-0.38
.amazonite3047-4731760.48-0.470.03
PG18viridian4248-4831770.48-0.480.03
PO48quinacridone burnt orange42635237350.480.400.28
..permanent green light4363-54321490.49-0.420.25
PG36phthalo green YS3957-54181620.49-0.470.15
PB36cobalt turquoise3948-45-172010.49-0.46-0.17
..permanent green deep3758-54221580.49-0.460.19
PY150nickel azo yellow67621461770.490.110.48
PR206quinacridone madder36605425250.500.450.21
PV49cobalt violet light505852-263340.500.45-0.22
PG21[emerald green]5961-57201610.50-0.480.17
PY117green gold5860-160910.51-0.010.51
PY175benzimidazolone lemon8365-864970.51-0.060.51
PY108anthrapyrimidine yellow72671465780.520.110.50
PG7phthalo green BS3151-5111780.52-0.520.01
PV32benzamida bordeaux30595618180.520.500.16
PB16phthalo turquoise2344-36-272170.52-0.42-0.31
PB36cerulean blue GS3552-39-342210.53-0.40-0.34
PV39blue violet20498-492790.540.08-0.53
PY184bismuth yellow8769-868970.54-0.060.54
PY40aureolin7769269880.540.020.54
.rhodonite36616013120.550.540.11
PO65methin nickel scarlet33645925230.550.500.21
PY1hansa yellow G8470170890.550.010.55
PY153nickel dioxine yellow71742969670.550.210.51
PV19quinacridone violet275858770.550.550.06
PR179perylene maroon29636021200.550.520.19
PB15:1phthalo blue RS2454-23-492450.56-0.24-0.51
PY35cadmium yellow lemon8972-1071980.57-0.080.56
PB36cerulean blue3758-36-452310.57-0.36-0.44
PY55+PY53diarylide yellow75772373730.570.170.55
PY37:1cadmium yellow deep71773468630.570.260.51
PY3hansa yellow light8873-1272990.58-0.090.57
PY65hansa yellow deep77782475720.580.180.55
..phthalo yellow green5579-53581330.58-0.400.43
PY151benzimidazolone yellow8475-175910.59-0.010.59
PY120benzimidiazolone yellow8075875840.590.060.58
..permanent green yellowish8675-1174990.59-0.090.58
PG50cobalt teal5659-56-191990.59-0.56-0.19
PB15:3phthalo blue2757-31-482370.59-0.32-0.50
PY35cadmium yellow81781178820.600.080.60
PY154benzimidazolone yellow8377177890.600.010.60
PY110isoindolinone yellow72763468630.600.270.54
PY35cadmium yellow light8677-277910.60-0.010.60
PY35cadmium yellow pale8677-477930.61-0.030.60
PY139isoindolinone yellow deep72773568630.610.280.54
PV15ultramarine violet (blue)2257-4-572660.61-0.04-0.61
PR176benzimidazolone carmine32706624200.610.580.21
PY138quinophthalone yellow8279079900.620.000.62
PR149perylene scarlet35746829230.620.570.24
PR216brown madder39746830230.620.570.25
PR122quinacridone magenta387171110.630.630.01
PY97hansa yellow8580-280910.63-0.010.63
PB15:3phthalo blue GS2860-36-482330.63-0.38-0.50
PR202quinacridone magenta33706912100.630.620.11
PO62benzimidazolone orange65775059500.630.410.48
PR214scheveningen red deep33746829230.630.580.25
PR264pyrrole carmine32736925200.640.600.22
PV19quinacridone rose44737213100.640.630.12
PR83alizarin crimson33737022170.640.610.19
PB33manganese blue4666-49-452230.65-0.47-0.44
PV19quinacridone red33757125190.650.610.21
PR106vermilion [genuine]47807138280.660.580.31
PO67pyrazoloquinazolone orange51836848350.660.540.38
PR108cadmium red deep36787328210.660.620.24
PR178perylene red35797328210.670.620.24
PO20cadmium orange60825958440.670.480.47
PB72cobalt blue deep2965-20-622520.67-0.21-0.64
PV42quinacridone pink35767416120.680.660.14
PB28cobalt blue3466-28-602450.68-0.29-0.62
PO69isoindoline orange55846652380.680.530.42
PR N/Aquinacridone carmine33797426190.680.640.22
PV7+PV15bright violet277365-323340.680.61-0.30
PO71pyrrole orange50857146330.680.570.37
PB17phthalo cyan3568-50-462230.69-0.50-0.47
PO34dizazopyrazolone orange54837144320.690.590.36
PR177anthraquinone red33807624180.690.660.21
PO5beta naphthol scarlet51877250350.700.570.40
PO36benzimidazolone vermilion48907649330.710.600.38
PR108cadmium red41867836240.710.650.30
PO43perinone orange53887252360.720.580.42
PR260vermilion extra42877936240.720.660.30
PO73pyrrole orange50947557370.730.580.44
PB29ultramarine blue2170-19-682540.73-0.20-0.70
PR170naphthol AS red38868130200.730.690.25
PR168anthraquinone scarlet44887939260.730.660.32
PR251pyrazoloquinazolone scarlet43908041270.730.650.33
PR209quinacridone red46868032220.740.680.27
PR9naphthol scarlet44898137250.740.670.31
PR255pyrrole scarlet44918141270.740.670.33
PR112naphthol AS red43918142270.750.670.34
PR108cadmium scarlet46918043280.750.660.36
PR242disazo condensation scarlet44968249310.760.650.39
PR188naphthol scarlet48928145290.770.670.37
PR254pyrrole red38948538240.780.710.32