Colorblindness and Usability
http://webword.com/moving/colorblindness.html

Follansbee, Todd
WebWord
2001

Abstract:

You might do a lot of usability testing on your web site but you still might lose up to 10% of your audience because of some simple mistakes with colors. Specifically, your web site may be designed in a way that doesn't work well for people with colorblindness. Generally the fix is quite simple: be sure to provide excellent contrast between your various web page elements.