Hue. Ten hues shown in spectral order from long wave red to short wave blue. Additive primaries for mixing color with light: red, green, blue

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1 Hue Ten hues shown in spectral order from long wave red to short wave blue. Additive primaries for mixing color with light: red, green, blue Subtractive primaries for mixing color with ink: cyan, magenta, yellow The colors shown in the hue circle vary in lightness. The example above shows the effect of holding lightness constant and changing only hue.

2 Lightness (value), a relative measure of brightness Typically used to show a progression, order from less to more

3 Saturation, vividness or purity of a color Desaturated to saturated, ranging from gray to more vivid purple Desaturated to saturated cyan; lightness and hue held constant in both examples Same hue, decreasing lightness, and increasing saturation. Both lightness and saturation decreasing. This set of reds ranges from light saturated to dark desaturated. Five hues with the same lightness and saturation with exception of yellow in second row. Think: Rhode Island. Saturation alone is rarely effective. Grayscale (lightness) is more effective. Use saturation to enhance lightness variation.

4 Three dimensional color specification Lightness varies vertically Hue varies radially Saturation (chroma) varies horizontally The solid is lopsided because the most saturated yellow is very light while the most saturated purple is relatively dark A vertical slice through the yellow and blue hues of the color solid. Notice: different shapes for purple blue (left) and yellow (right). Notice: colors increase in saturation (chroma) away from the central axis of neutral grays.

5 Color specification

6 Sequential color schemes: progression, order

7 Diverging color schemes: change or difference from a midpoint

8 Qualitative color schemes: categorical difference

9 Color vision impairment Many of these colors will look the same to colorblind map readers. The road, track, and town colors will all look like each other and will be difficult to distinguish from the background. The pink for the hypothetical ferry routes is likely to look the same as the surrounding cyan water.

10 Color vision impairment An example of how to use the colorblind confusion diagram. Choose colors separated by at least a zone or that are different in lightness. The selected red orange yellow colors (with black outlines) are from the same zone but differ in lightness. The blues and reds of similar lightness are two or more zones apart.

11 Color vision impairment The red, orange, and green on the left are likely to look the same. On the right, the qualitative scheme has been redesigned with greater lightness differences and careful hue choices. Yellowgreen brown would be confusing but they are different in lightness. Blue and purple also differ in lightness. Color pairs with similar lightness (purple green and blue brown) are well separated on the confusion diagram.

12 Simultaneous contrast Color X matches D, though its dark surround makes it look like C, a lighter color. Color Y matches B, though simultaneous contrast makes it look like A.

13 Simultaneous contrast The gray tracks shift toward blue because they are surrounded by yellow. The blue ferry routes shift lighter and yellow, so they look grayish because they are surrounded by a darker blue. The yellow roads shift lighter and bluer, so they look like a very light gray. Moral: There is no substitute for examining the map in the final output format