chromatism vs iridescence

chromatism

noun
  • The state of being coloured 

  • chromesthesia 

  • chromatic aberration 

iridescence

noun
  • The condition or state of being iridescent; exhibition of colors like those of the rainbow; a prismatic play of color. 

  • Any shimmer of glittering and changeable colors. 

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