unpigmented vs unstained

unpigmented

adj
  • Not pigmented. 

unstained

adj
  • Not dyed or discolored; not marred by any stains, marks, or spotting. 

  • Pure, pristine, clean, immaculate, unadulterated. 

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