If you want to see how your web page looks to people who are color blind, check out: http://colorfilter.wickline.org/.

Their site gets the web page from a URL you enter and then applies color filtering to it so that you can see how people with various types of color blindness will see your page. The page rendering is real-time (although a little slow) and once the page is rendered, they include a little widget that allows you to select from different types of color blindnesses and other visual deficiencies.

This site is a nice way to ensure that your text/background color combination does not result in unreadable text for those with color blindness.