Milli had a little white on her feet and chest as a puppy, which has turned to tan as she's grown. I think it's cute! Someone told me that they're just going to be a "lighter" yorkie when they have white toes and a little white star on their chests.
A little can be "multi-sired"-I had to complain about a breeder once for registering the litter as all purebred AKC yorkies when there was a good chance they were part rat terrier! She was trying to pass them off as purebred yorkies...
Here's a link to AKC's multi-sired litter info:
http://www.akc.org/dna/multisire.cfm