On Vision and Colors from a prism, however, the production of white can be demonstrated by using a mixture of colored light from each of the three main pairs of complementary colors: red – green, orange – blue, or yellow – violet. White can be produced from two complementary opposite colors when both of the external causes of the colors excite the same retinal place at the same time. Newton claimed that white could be produced by the aggregation of his seven prismatic colors. He erroneously considered color to be in light instead of in the eye. White is the result of the combination
On Vision and Colors that were exhausted by the whiteness become completely inactive. The retinal positions that had been rested are now easily stimulated. This explains afterimage (physiological spectra). Both Goethe and Schopenhauer use the word "spectrum" [Spektrum], from the Latin word "spectrum" meaning "appearance" or "apparition," to designate an afterimage. If, instead of white, we stare at yellow, then the afterimage, or physiological color spectrum, is violet. Yellow, unlike white, does not fully stimulate and exhaust the retina's activity. Yellow partially stimulates points on the retina and leaves those points partially unstimulated. The retina's activity has been qualitatively divided and separated into two