chroma vs chromism

chroma

noun
  • A note in a chromatic scale 

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

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

chromism

noun
  • chromatism 

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