According to research, about 10.5 million people suffer from color blindness.  I have found a site that allows you to perceive web sites as you would if you were color blind.  Not a practical web site for sure, but kind of interesting.  Enter the website address and choose from various forms of color blindness from the drop down box and the site you go to is transformed into a simulation of what a color blind person sees.  It takes some time to render the page depending on how graphic intensive it is, but it is a rather fun experience.  Check out wp3.lockergnome.com as seen by the color blind.  Check it out HERE.