Try the following sites. It can be difficult to keep up with the variations in coat colors and varieties, and these will give you some good pictures to work off of to determine what kind of rattie you have.

For examples of most colors and patterns, visit the RMCA's standards at
<http://www.rmca.org/Standard/Rat/ratidx.htm#example>

Some other good sites to try are:
<http://www.altpet.net/rodents/rats/rf03.html>
<http://www.afrma.org/fancyrm.htm>
<http://www.nfrs.org/nfrsvars.html>
<http://members.dingoblue.net.au/~farrall/bruce/colours.html>