Fig. 15 Measurement of intrinsic saturation of spectrum colors for normal, deuteranomalous, deuteranopic, protanomalous, and protanopic observers. For normal observers, wavelengths in the region of 570 nm appear most like white, whereas the ends of the spectrum are least like white. Note that for dichromats (deuteranopic and protanopic), one part of the spectrum is indistinguishable from white. Note also that poorest saturation for the anomalous trichromats is in the blue–green region; protanomals have least color saturation close to 490 nm, whereas the deuteranomals' region is closer to 500 nm. (Adapted from Chapanis A: Spectral saturation and its relation to color-vision defects. J Exp Psychol 34:24, 1944.)