In Photoshop CS4 how do I convert a picture into those artsy negatives that use less colors?

for ex.....I want to take a picture where all the colors are subsidized to just the outline so the picture looks the same while only using say 2 colors......red and white, red is the backround, white is all major outlines to figure a face......In Photoshop CS4 how do I convert a picture into those artsy negatives that use less colors?
Try one of Mama Shan's colorizing/toning videos. I think you're looking for the ';black and white adjustment'; tutorial. It's about removing saturation, but has tips on colors.