Universal Principles of Color

98UNIQUE HUES

Colors considered to be perceptually pure without any evidence of other hues

Ewald Hering first defined the unique hues, sometimes known as psychological color primaries, as red, green, yellow, and blue. Hering’s observation was that these four colors cannot be simultaneously perceived. Unlike the unique hues that appear pure, other colors always appear as combinations of these unique hues. For example, orange can be perceived as a mixture of red and yellow.

Hering’s system is based on two sets of opposite or opponent colors: red/green and yellow/blue. These two pairs of opponent colors, along with a white/black pair, form the ...