bicolour vs dichromatic

bicolour

adj
  • Having two colours 

noun
  • A flower, cat etc., that has two colours. 

  • A flag with such colours, consisting of two stripes that are either vertical or horizontal. 

dichromatic

adj
  • having two colors. 

  • having two independent channels for conveying color information in the eye. 

  • having two hues, either of which may be visible depending on both the concentration of the absorbing substance and the depth or thickness of the medium traversed, such as in pumpkin seed oil. A form of polychromatism. 

  • exhibiting dichroism; dichroic. 

  • occurring or existing in two different ornamentations or colors, typically as a form of sexual dimorphism. 

  • having a form of colorblindness in which only two of the three primary colors can be distinguished 

How often have the words bicolour and dichromatic occurred in a corpus of books? (source: Google Ngram Viewer )