auburn vs black as Newgate's knocker

auburn

adj

  • Of a reddish-brown colour. 

noun

  • A dark reddish-brown colour, often used to describe hair colour. 

black as Newgate's knocker

adj

  • Completely black in colour. 

How often have the words auburn and black as Newgate's knocker occurred in a corpus of books? (source: Google Ngram Viewer )