色彩論
Thomas Young postulated that the eye contains receptors that respond to three different primary sensations, or spectra of light. James Clerk Maxwell showed that all hues, but not all colors, can be created from three primary colors such as red, green, and blue, if they are mixed in the right proportions. Goethe's "Theory of Colours" provided the first systematic study of the physiological effects of color (1810). His observations on the effect of opposed colors led him to a symmetric arrangement of his color wheel anticipating Ewald Hering's opponent color theory (1872).