chromaticity vs iridescence

chromaticity

noun
  • An objective specification of the quality of a colour, regardless of its luminance. 

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 chromaticity and iridescence occurred in a corpus of books? (source: Google Ngram Viewer )