Spectral response curves of normal and color-defective subjects were determined with the method of electric stimulation of the eye. The curves of anomalous trichromats consist of four components R, Y, G, and B, among which either R or G is especially weak. The curves of dichromats consists of three components; R and G are missing in the protanope and the deuteranope, respectively. The three kinds of response in the color-blind are definitely small compared with the corresponding normal responses. The magnitude of response of anomalous trichromats is intermediate between the normal and the color blind. Hue discrimination curves were obtained from one and the same subjects under comparable experimental conditions and interpreted in terms of spectral responses. From these experiments it was concluded that the yellow component plays a very important role in hue discrimination of color-defective subjects, whereas it is not so important for normal hue discrimination.
KOITI MOTOKAWA and KOSAKU ISOBE, "Spectral Response Curves and Hue Discrimination in Normal and Color-Defective Subjects," J. Opt. Soc. Am. 45, 79-87 (1955)