cobalt blue vs navy blue

cobalt blue

noun

  • A deep blue pigment derived from cobalt; zaffre. 

adj

  • Of the color of the pigment zaffre. 

navy blue

noun

  • A dark blue color. 

adj

  • Having a navy blue color. 

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