On the ArcGIS Blog, Heather White has a series of video-tutorial posts exploring how to choose colour¹ when making maps, and what colours can signify on a map. From Color connotations and associations: “Colors are never neutral. They affect how people think and feel about your map. As a cartographer, you should be aware of the connotations and associations carried by the colors you use. They can be powerful tools to help you communicate more clearly. But if you ignore them, they can just as easily sabotage your map’s message.” See also Light and dark color schemes and Choose similar colors to map similar things (which you’d think would go without saying, but then things that ought to go without saying almost always need saying).

1. I’m Canadian and spell it with a u; it should go without saying that I retain original spellings in titles and quotes.