blue-red vs purple dye murex

blue-red

noun
  • A colour between blue and red; purple or crimson. 

adj
  • Of a colour between blue and red; purple or crimson. 

  • Consisting of the colours blue and red individually. 

purple dye murex

noun
  • A species of medium-sized predatory sea snail, Haustellum brandaris, which secrets a substance that can be used to make a long-lasting purple dye- Tyrian purple. 

How often have the words blue-red and purple dye murex occurred in a corpus of books? (source: Google Ngram Viewer )