I mentioned to one of the other guys at the table that there was a recent blog post that covered the subject very well, providing examples of what color blind vision is like. Check it out at Critique Wall.
Vischeck, a site mentioned in the article, simulates colorblind vision. Even better, Daltonize corrects images for colorblind viewers. The images will still look different compared to what we see but colorblind folks will be able to discern that there are different colors in the images. "The 'true' color of something may be irrelevant but the fact that it is different from its surroundings is very important."