chroma vs polychromasia

chroma

noun
  • The aspect of a colour's hue that depends on the amount of white or black in it; saturation 

  • A note in a chromatic scale 

  • The colorfulness relative to the brightness of a similarly illuminated area 

polychromasia

noun
  • A disorder in which there is an abnormally high number of red blood cells in the bloodstream as a result of their having been prematurely released from the bone marrow during blood formation. 

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