This section is rather incomplete, and is likely to remain that way until I have the need (or simply the spare time) to investigate colour printing with LaTeX for myself. Section 7.3 of the LaTeX\ User's Guide contains a small blurb on how to include colour. As best I can figure, in order to use these commands, you will need to include the following line in the preamble of your document:
\usepackage{color}
It seems that xdvi cannot handle previewing of colour generated with this package, all I got when testing it was an opaque box where a red box with text in it was supposed to be. After converting the document to Postscript, however, ghostview was able to view it correctly.