dark blue vs merchant marine

dark blue

noun
  • A deep, dim blue colour: navy or similar. 

  • A member of the Oxford rowing team. 

merchant marine

noun
  • A ship dedicated to commercial, rather than military, purposes. 

  • Synonym of merchant navy. The fleet considered as an entire combined force. 

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