virescent vs viridian

virescent

adj

  • Green-like, greenish. 

  • Becoming green. 

viridian

adj

  • Of a bluish green colour. 

noun

  • A bluish-green pigment made from chromium sesquioxide. 

  • A bluish-green color. 

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