Here's a site that explains the different registries.
Registries. You can get a "parti" looking dog by mixing a Yorkie with a maltese or other breed, and since unethical breeders have tried to cash in on the current popularity of the parti, you have to be very careful. I personally don't believe a breeder should try to bring more "variety" into a breed, but if you want a true parti, you should buy from someone, who is at the very least, is registered with the AKC, the other registries take the breeders word for it and this is worthless.
APRI - AMERICA'S PET REGISTRY INC. Advertises free registration for commercial breeders. Non Profit 'dedicated to the preservation of the professional pet industry', dogs and cats. Founded by retailers of pets (commercial breeders and resellers).
CKC-Continental Kennel Club (do not confuse with Canadian Kennel Club!)
CKC will recognize a cross between any two purebred dogs, and will issue a registration certificate on their offspring. These crosses are not registered as purebred dogs but are registered as the offspring of purebred dogs. CKC accepts no responsibility for any inaccurate, false, or fraudulent information submitted on registration applications. They sponsor no shows or championships. They also give big fee breaks to large kennels registering lots of dogs (such as Puppy Mills). Will register dogs not registered with other recognized registries.