Ametameric
A 16 color palette for dichromats and trichromats
Ametameric is as a system palette that provides the standard CGA/ANSI colors accomodating various forms of human color blindness/color vision deficiencies. 16 colors (including white, black and two grays) that all provide sufficient contrast for all common types of color vision. For use in terminals and as a color set for lines in charts/visualization, for further palettes that work well (only) for red/green color vision anomalies Paul Tol's Color schems and templates. is valuable.
The following chart shows all color combinations. If ametameric works as intended only the intersections on the diagonal from top-left to bottom-right should be blending into each other; being nearer each other than many other color pairs is OK. Being practically impossible to discern presence of shape when used for text on each other is not.
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The 8bit sRGB palette values and corrsponding color values in CIE Lab and CIE Lch:
| idx | name | hex RGB | dec RGB | CIE Lab | CIE Lch |
|---|---|---|---|---|---|
| 0 | black | #000000 | 0, 0, 0 | 0, 0, 0 | 0, 0, 0 |
| 1 | red | #7f0521 | 127, 5, 33 | 27, 48, 22 | 27, 53, 25 |
| 2 | green | #48a04b | 72, 160, 75 | 59, -41, 36 | 59, 54, 139 |
| 3 | brown | #a36000 | 163, 96, 0 | 48, 24, 56 | 48, 60, 67 |
| 4 | blue | #0a0aaa | 10, 10, 170 | 19, 48, -81 | 19, 94, 301 |
| 5 | magenta | #9131be | 145, 49, 190 | 41, 56, -56 | 41, 80, 315 |
| 6 | cyan | #3282ae | 50, 130, 174 | 51, -14, -31 | 51, 34, 246 |
| 7 | bright-gray | #a7a7a7 | 167, 167, 167 | 68, 0, 0 | 68, 0, 0 |
| 8 | gray | #585858 | 88, 88, 88 | 37, 0, 0 | 37, 0, 0 |
| 9 | bright-red | #ff9b82 | 255, 155, 130 | 74, 36, 30 | 74, 47, 39 |
| 10 | bright-green | #5af5a0 | 90, 245, 160 | 87, -57, 28 | 87, 64, 153 |
| 11 | yellow | #ffe600 | 255, 230, 0 | 91, -4, 89 | 91, 89, 93 |
| 12 | bright-blue | #0000ff | 0, 0, 255 | 30, 68, -112 | 30, 131, 301 |
| 13 | bright-magenta | #de90f2 | 222, 144, 242 | 71, 42, -37 | 71, 56, 318 |
| 14 | bright-cyan | #8ed0fd | 142, 208, 253 | 80, -13, -29 | 80, 32, 246 |
| 15 | white | #ffffff | 255, 255, 255 | 100, 0, 0 | 100, 0, 90 |
Downloads
| ametameric.gpl | GIMP Palette |
| ametameric.esc | initializes ametameric as the 16 system colors, reset foreground/background. |
| ametameric-reverse.esc | initialize ametameric as the 16 system colors, but with dark on bright text. |
| ametameric-desaturated.esc | The ametameric palette linearly combined in XYZ space with its corresponding luminance by a factor of 0.85. The internal color relationships remain as in the base ametameric palette. This is also useful with wide gamut displays to avoid super-saturated colors in the part of the gamut that is wider than normal in non-color managed terminal emulators. |
user@host:~$ curl https://pippin.gimp.org/ametameric/ametameric.esc Ametameric 20200423 user@host:~$
If it works the colors of the terminal will change, note that most terminal emulators on linux are not color managed; thus with a widegamut display this will yield over-saturated colors.
Color Blindness Simulation
The following grids show the same grid og all combinations through dichromat simulation, using the tables from Martin Krzywinski's Color Palettes for Color Blindness page. These are different from the color vision deficienct simulator in GIMP as well as different from the Coblis on color-blindness.com, so both of these have additionally been used in verification; being in agreement with all of these hopefully means that discrimation is also achieved in human dichromats.
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Colors ordered by difference importance
Excluding black and white as colors - and using them as possible backgrounds. An order of introducing colors that continuously maintains a high level of contrast (useful for additional lines in charts, bar diagrams etc.):
License
The palette values of (ametameric, by Øyvind Kolås), identified by Øyvind Kolås, is free of known copyright restrictions.
Though attribution is not neccesary; using the name of the palette and attribution in the form of links to this page is appreciated.
Design process
As an emergent guide through the manual optimization process, two 2dimensional gamuts for dichromats appeared, one for the red/green deviances protanopia and deuteranopia, and another for tritanopia.
The two 2d gamuts split the colors into three groups, grays, cold and warm colors. For tritanopia the cold shades are blue and warm are red, while in the simulated gamutes for protanopia and deuteronopia the warm patches have a yellow tint.
In addition to these visualization aids, an optimizer that scores the 5 worst pairs using a cross-observer color difference metric is used to do small permutation on an input iteration with the worst collisions taken away, permiting rapid though very manual iteration of possibly better solutions.
Some humans are actually color blind and have achromatic vision, I am not sure if that corresponds to luminance as seen by the normal observer, but effort has been made to ensure each slot in the palette have a different luminance, preserving contrast upon conversions to grayscale; like sometimes when printing.
NOTE:This page relies on background/text color specified in CSS being interpreted as sRGB and correctly converted to display. Otherwise colors will be oversaturated on wide-gamut displays; the desired dichromat discrimination probably still works though.
Exhaustive Text fg/bg tests
white
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
black
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
dark-gray.
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright gray
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
blue as in midnight commander
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
red
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
green
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
brown
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
magenta
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
cyan
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright red
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright green
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
yellow
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright blue
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright magenta
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.
bright cyan
black red green brown blue magenta cyan bright gray dark gray bright red bright green yellow bright blue bright magenta bright cyan white.