http://www.partiyorkies.com/ also
http://www.crownridgegems.com/
The above sites went through heavy DNA testing to prove its pedigree origination and has been deemed 100% AKC Yorkshire Terrier, that being said AKC allows the registration of the particolored yorkie.
Any website can put up what ever they want BUT facts are fact the piebald gene is from the yorkshire terrier.
COLOR: The prime pre-requisite of fine diamonds is also our prime goal. Our rare Parti-color AKC registered Yorkshire Terriers are marked to perfection. Their eyes are masked in black and tan, and their eyelids and noses are properly pigmented. Their glowing white coats are complemented by black saddles or perhaps a few black spots interspersed in the iridescent-white, flowing hair. from Crownridgegems.com
The well versed member here on the parti gene is Whispersmom you may want to contact her she owns both Parti and Biewer.