Color rules
It seems slightly ironic to discuss color rules in a book that will be printed in black and white (of course, that may not be true if you are reading this book on an electronic device). Nevertheless, even in a monochromatic setting, a discussion of color is relevant. For example, exclusive use of black text communicates something different than using variations of gray. The following survey of color rules should be helpful for ensuring that you use colors effectively in a variety of settings.
Keep colors simple and limited
Stick to the basic hues and provide only a few (perhaps three to five) hue variations. In his book, The Functional Art: An Introduction to Information Graphics and Visualization, Alberto Cairo provides insight as to why this is important:
"The limited capacity of our visual working memory helps explain why it's not advisable to use more than four or five colors or pictograms to identify different phenomena on maps and charts."...
