dichromatism

noun

1. (countable, uncountable)The condition of being dichromatic
2. (countable, uncountable)A form of colourblindness in which only two of the three primary colours can be distinguished
3. (countable, uncountable)The condition when male and female birds have different plumage colors.

   “There long had been a bias among researchers to think of the evolution of sexual dichromatism as driven by changes in male coloration.”