dichromatismn.

1836 J. F. W. Herschel Diary 7 Dec. in D. Evans Herschel at Cape (1969) 266 Also shewed the Dichromatism of the Tincture of Ianthina.

1865 Zoologist 23 9744 Mr. J. J. Weir suggested that ‘dichromatism’, a ‘dichromatic variety’, would denote the phenomenon in question.

1884 E. Coues Key to N. Amer. Birds (ed. 2) 656 Remarkable differences of plumage in many cases, constituting dichromatism, or permanent normal difference in color.

1943 O. Stuhlman Introd. Biophysics iv. 152 The color of a solution is composed of two or more maxima of transparency, and, if the rate of change of these maxima is not the same, dichromatism occurs with change in concentration.

1999 Amer. Naturalist 154 182 The fact that estrogen-dependent dichromatism is ancestral in extant birds suggests that more brightly colored monochromatism may have been ancestral in modern lineages of birds.

1859 Philos. Trans. (Royal Soc.) 149 336 I do not hesitate to record my own impression that the cases of perfect dichromatism are much more common than Dr. Wilson supposes.

1895 E. B. Titchener tr. O. Külpe Outl. Psychol. 133 There are then three possible forms of dichromatism: red blindness, green blindness, and violet blindness.

1910 Proc. Royal Soc. 1909–10 B. 82 463 The defect which has caused the non-perception of certain red rays has not caused the dichromatism.

1959 New Scientist 30 Apr. 972/2 In dichromatism, the colour-blind subject requires only two primaries in order to match any spectral colour.

2004 T. Fraser & A. Banks Designer's Color Man. i. ii. 28/1 Most color deficiencies affect the L-cones or the M-cones, and the most severe deficiencies, when one cone type is completely absent, are collectively termed dichromatism, since only two color receptors remain.