Population distributions obtained on the Nagel anomaloscope by Nelson and by Schmidt are considered. The role is discussed of inert pigments in the variability of matches on the Nagel anomaloscope and on anomaloscopes for the detection of tritanomaly. Since lens pigmentation varies systematically with age its effect can be calculated. Macular pigmentation, however, varies unpredictably between subjects and its effect in a Blue + green = Bluegreen color match can be nullified only if the mixing primaries are chosen at wavelengths for which the macular pigment densities are equal.