The ICHR is a good resource for finding out more information about the Champagne Dilution gene. It can look alot like the dun and cream genes but there are differences that can aide you in identifying a champagne horse.
Speckled skin (similar, but different that the mottled skin of an appaloosa)
Pink skin (if a horse being lable as a palomino has pink skin instead of black skin - then it is may be champagne)
Hazel eyes
