I'm not sure what kind of bike you have, but there's a company called 'second look' that makes a bunch of seat 'skins' that's popular.
IMO colormatching seats looks tacky since it's almost impossible to match vinyl with painted plastics.
anyway, you could get a bunch more answers if you run a couple searches first, the search button is the third one in from the right, on the sbn toolbar on the top.