Any sight that could be roughly described as reddish or greenish is called an organic chromatic sensation. We use words like red, green, pink, chartreuse, crimson, turquoise, orange, purple, olive, scarlet, khaki, magenta etc. to identify particular visual sensations within the organic category. Ewald Hering reports that, “No colour is clearly reddish as well as greenish … redness and greenness … are mutually exclusive.”1Ewald Hering, Outlines of a Theory of the Light Sense, page 49. Translated by Leo M. Hurvich and Dorothea Jameson. Harvard University Press, 1964. Therefore organic visual sensations are capable of binary description.
The reference experience for describing these sensations is seeing blood. So to make a binary description of an organic chromatic sensation, compare it to seeing blood. Report the result using one of the following algebraic statements. If the two experiences are not comparable, then say that the sensation is not an organic chromatic sensation and express this as If the sensation is like seeing blood, then say that it is red. Express this as If not, then say that it is green and that The number is called the redness. These relations are expressed mathematically as