https://cran.r-project.org/web/packages/pals/vignettes/pals_examples.html http://geog.uoregon.edu/datagraphics/color_scales.htm https://github.com/EmilHvitfeldt/r-color-palettes http://www.fabiocrameri.ch/colourmaps.php http://bids.github.io/colormap/ http://colorbrewer2.org http://pantone.com/ http://www.ral.de/