Off colors like parti (chocolate and Golden too) have been in the breed since the beginning. Foundation dogs who began this breed may have been blue and tan in color but many carried the recessive genes for different colors that were passed down from previous generations.
The parti color, was denied registration until 2000, when 2 ladies in California
fought to get the parti colored pups coming out of the Nikkos line registered. AKC DNA'd 42 litters, and as many living relatives (parents, grandparents ...) to verify that the parti pups were purebred yorkies. Numerous old time, well known breeders were interviewed to see if they had ever had a parti color show up in their breeding program and it was determined that this color is in the genetic makeup of some of our yorkies.
There are references from the early 1900's that white yorkshire terriers were around, but the most interesting piece I've found regarding white yorkies, is in this book:
A manual of toy dogs: how to breed, rear, and feed them By Mrs. Leslie Williams (written in 1904)
"The white Yorkshires, a new variety some folk have tried to push, is, I think, in no way especially desirable—the Maltese can do all that is necessary in that line; while the attempt to make " silver " Yorkshires popular, too, simply means that bad-coloured dogs without any tan (paleness of tan is the stumblingblock in many a Yorkshire's career), are classed by themselves and offered prizes."
Ernest Hemingway's Grandfather owned a white Yorkie named Tassel in the early 1900's and there are published writings during that same time period, indicating white yorkshire terriers were being shown at various State agricultural shows.
Early Kennel Club and American Kennel Club records, in addition to black and tan, blue and tan, blue and gold and black and gold also lists "dark tan," "black," and "blue" as some of the colors seen and registered in the yorkshire terrier breed, back in the earlier days.
So off colors have always been in this breed, they've just been swept under the rug, given away or destroyed because until the year 2000, they were denied registration with AKC.
Hope this info helps
