blue-gray vs sapphire

blue-gray

adj
  • Of a bluish grey color. 

sapphire

adj
  • of a deep blue colour. 

  • pertaining to a 45th year 

noun
  • Any of the butterflies in the southern Asian lycaenid genus Heliophorus. 

  • Any hummingbird in the genera Hylocharis and Chlorestes, as well as the rufous-throated sapphire, which is now in the genus Amazilia. 

  • A clear deep blue variety of corundum, valued as a precious stone. 

  • A deep blue colour. 

  • A white, yellow, or purple variety of corundum, either clear or translucent. 

How often have the words blue-gray and sapphire occurred in a corpus of books? (source: Google Ngram Viewer )