black mark vs discoloration

black mark

noun
  • something that negatively affects someone's reputation 

discoloration

noun
  • The act of discoloring, or the state of being discolored; alteration of hue or appearance. 

  • A discolored spot; a stain. 

How often have the words black mark and discoloration occurred in a corpus of books? (source: Google Ngram Viewer )