Reference:
  Author: Achim Zeileis and Kurt Hornik and Paul Murrell
  Title: "Escaping RGBland: Selecting Colors for Statistical Graphics"
  Journal: Computational Statistics & Data Analysis
  Year: 2009
  Volume: 53
  Pages: 3259--3270
  DOI: 10.1016/j.csda.2008.11.033
