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 insuring that you use colors effectively in a variety of settings.
Color rules
Rule: 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...