coloration vs undertone

coloration

noun
  • The quality of being colored. 

  • The act or art of coloring. 

  • Ornamental division (also called passaggi, glosas, diminutions. etc.) employing rapid black notes. 

  • A notational device for indicating hemiola through either use of red ink (in mensural black notation) or black noteheads (in mensural white notation). 

  • Political tendency. 

undertone

noun
  • A pale colour, or one seen underneath another colour. 

  • A low state of the physical faculties. 

  • An implicit message perceived subtly alongside, but not detracting noticeably from, the explicit message conveyed in or by a book, film, verbal dialogue or similar (contrast with overtone); an undercurrent. 

  • An auditory tone of low pitch or volume. 

verb
  • To accompany as an undertone. 

  • To say or speak in an undertone. 

  • To present as less important, noticeable or prominent. 

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