In comments on a previous post, Igor Asselbergs points to a page on Using Color In Information Graphics from the NASA/Ames Color Research Lab. In addition to a very large collection of articles/tutorials on effective (and ineffective) uses of color in representing information graphically, there’s also a Java-based Color Tool:
“The Color Tool is designed to provide the designer with views of the perceptual relationships among the possible color choices. It improves on previous tools by more clearly representing the constraints imposed by the physical display and the structure of human color vision. This should help the designer manage the luminance contrasts of symbol and background colors by showing the tradeoffs in hue and saturation.” – from the website. One nice feature is the ability to change the background luminosity, and see how that affects the perception of the various colors.