The Practical Color Coordinate System (PCCS) is a discrete color space developed by the Japan Color Research Institute in 1964. PCCS is notable for indexing colors by just two characteristics, hue and tone, as opposed to the three (hue, value, and chroma) traditionally used by systems such as the Munsell color system.

Hue PCCS defines 24 gradations of hue, arranged to be perceptually equal. These hues are determined based on the psychological primaries (●) and their psychological complements (○) as well as the additive and subtractive primaries (△).

Procedure Hue Number:Symbol Name Notes 　 1:pR Purplish red ● 2:R Red △ 3:yR Yellowish red Additive primary red. 　 4:rO Reddish orange 　 5:O Orange ○ 6:yO Yellowish orange 　 7:rY Reddish yellow ● △ 8:Y Yellow Psychological & subtractive primary yellow. 　 9:gY Greenish yellow 　 10:YG Yellow green 　 11:yG Yellowish green ● △ 12:G Green Psychological & additive primary green. 　 13:bG Bluish green ○ 14:BG Blue green 　 15:BG Blue green △ 16:gB Greenish blue Subtractive primary cyan. 　 17:B Blue ● 18:B Blue Psychological primary blue. △ 19:pB Purplish blue Additive primary blue. ○ 20:V Violet 　 21:bP Bluish purple 　 22:P Purple 　 23:rP Reddish purple ○ △ 24:RP Red purple Subtractive primary magenta.

Upon comparing two hues, the difference in hue number can be used to determine the following relationships. Difference Relationship Corresponding hues when based on red（■ 2:R) 0 Same hue ■ 2:R 1 Adjacent hues ■ 1:rP, ■ 3:rY 2–3 Similar hues ■ 4:rO, ■ 5:O, ■ 23:rP, ■ 24:RP 4–7 Intermediate hues ■ 6:yO, ■ 7:rY, ■ 8:Y, ■ 9:gY, ■ 19:pB, ■ 20:V, ■ 21:bP, ■ 22:P 8–10 Contrasting hues ■ 10:YG, ■ 11:yG, ■ 12:G, ■ 16:gB, ■ 17:B, ■ 18:B 11 Adjacent complementary hues ■ 13:bG, ■ 15:BG 12 Complementary hue ■ 14:BG

Tone PCCS defines 12 tones and 5 achromatic greys based on Munsell categorizations of lightness and chroma. Colors within the same tone category will have a similar quality regardless of hue. Lightness ranges from 1.5 (black) to 9.5 (white), while chroma ranges from 0s (achromatic) to 9s (pure color).

9.5 W p lt 　 ltGy b 　 ltg sf v 5.5 mGy s 　 g d 　 　 dkGy dp 　 dkg dk Lightness 1.5 Bk 　 Saturation 0s 1–3s 4–6s 7–8s 9s

Classification Tone Symbol Name Light pure color (tints) p Pale lt Light b Bright Pure color v Vivid Dark pure color (shades) dp Deep dk Dark dkg Dark greyish Intermediate tones (tones) ltg Light greyish sf Soft s Strong d Dull g Greyish

"Vivid" colors are pure colors and represent the highest possible chroma for their respective hue. Light pure colors (pale, light, and bright) result from mixing the pure color with only white. Dark pure colors (deep, dark, and dark-greyish) result from mixing the pure color with only black. The intermediate colors (light greyish, soft, strong, dull, and greyish) result from mixing the pure color with both black and white.

These charts use reddish orange (■ 4:rO) as the example hue. 4:rO has a vertically symmetrical hue plane because the pure color has a lightness of about 5.5. This is not the case for all hues; pure colors with high lightness (e.g. ■ 8:Y) or low lightness (e.g. ■ 20:V) have accordingly skewed hue planes. Despite this difference in lightness, all pure colors are considered "vivid." In general, tone categories are meant to group colors that give a similar impression, so colors within a tone category do not necessarily have matching lightness or chroma.

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