A rat's coat is considered straight or standard if it lies flat and smooth on the rat's body. Rex rats have curly or wavy coats and whiskers that curl at the tips. Satin rats have shiny, silky hair and longer than average coats. Rats come with as many as 32 different hair colors. Rat colors range from the common black or white, to the slightly unexpected chocolate or agouti, to the positively outrageous powder blue or platinum. Silvered rats have an equal number of silver hairs as primary color hairs, giving them a sparkling appearance.
There are almost as many different coat markings as there are color variations. Hooded rats (with their dark heads and long straight stripes down their spines) and Irish rats (with their solid color tops and white bellies) bear some of the most common markings, though you can also find Dalmatian rats, blaze rats, masked rats, and many more.
To learn more, read Choosing a Rat.