bicolour vs polychrome

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. 

polychrome

adj
  • Using multiple colours 

  • Executed in the manner of polychromy 

verb
  • To divide (a dye etc.) into multiple colours. 

  • To paint or dye with multiple colours. 

noun
  • A piece of multicolored pottery. 

  • esculin (so called in allusion to its fluorescent solutions) 

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