Abstract

Hering’s opponent-colors theory suggests that our color sensations are produced by three mechanisms: a red–green mechanism, a yellow–blue mechanism, and a white–black mechanism. The first two mechanisms give rise to our sensations of hued colors; the third mechanism gives rise to our sensations of hueless colors. Noticeably, whereas the pair of colors produced by each of the hued mechanisms do not mix to yield a phenomenal intermediate (i.e., there are no greenish reds, reddish greens, yellowish blues, or bluish yellows), the colors produced by the hueless mechanism, white and black, do have a phenomenal intermediate—gray. This different behavior of the white–black mechanism poses a problem for Hering’s theory. Several attempts to fix this problem have been suggested. This paper focuses on the suggestion made by Paul Heggelund a century after Hering proposed his theory. In Heggelund’s amendment of Hering’s theory, the hueless colors are not confined to the one-dimensional gamut between black and white, but rather require two components for their full description: a light–dark (or luminous–black) component, where light and dark are mutually exclusive sensations, and a white component, which doesn’t have an opponent counterpart. Here I show that although Heggelund’s theory indeed provides a solution to the problem that the hueless colors pose to Hering’s theory, it is not self-consistent. I go on to revise Heggelund’s theory to obtain a consistent opponent-colors theory.