I love hairless, I love selfs, that would be, solid color rats, and I love agouti colors, which would be kindof a wild brown.
There are really cool breeds like a Siamese. Those look awsome, like a PEW (albino with pink eyes), but with a little coloring around their noses and feets.
There is a breed unique to Europe, and I forget the name, but they look awsome, kindof striped, like a racoon, but over the entire body.