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. Author manuscript; available in PMC: 2024 Sep 1.
Published in final edited form as: Trends Cogn Sci. 2023 Jul 1;27(9):791–804. doi: 10.1016/j.tics.2023.06.003

Figure 1. Opponent-Colors Theory.

Figure 1.

Diagram by Ewald Hering illustrating Opponent-Colors Theory. According to Hering, “the six basic sensations of the visual substance are arranged in three pairs: Black and white, blue and yellow, green and red. Each of these three pairs corresponds to a distinct process of dissimilation and assimilation, such that the visual substance can undergo chemical or metabolic change in three different ways” ([2], §. 42.). In the top panel, “r” is red, “b” is blue, and the ratios indicate the combinations of these components in each color mixture of the bottom panel. So, purple has a ratio of blue to red (b:r) of 0.5:0.5. Hering’s theory boils down to two ideas (1) that the appearance of any color is necessarily and sufficiently described by the extent to which it is reddish-versus-greenish, bluish-versus-yellowish, and blackish-versus-whitish; and (2) that these appearance mechanisms are hardwired in the nervous system.