colour in vs fresco

colour in

verb
  • To colourise; to add colours to a black-and-white drawing, using coloured drawing equipment. 

fresco

verb
  • To paint using fresco. 

noun
  • The technique used to make such an artwork. 

  • A cool, refreshing state of the air; coolness, duskiness, shade. 

  • An artwork made by applying water-based pigment to wet or fresh lime mortar or plaster. 

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