Here are a few links that challenge some of the views posted in this thread and a few new points, to make us all wonder ...
The YTCA's website calls Parti yorkies "Designer dogs"
Yorkshire Terrier Club of America (Awards)
A portion of the YTCA's website article (also posted in post #1 of this thread in Gale Thompson's " Parti-Color Yorkshire Terriers" article) states:
A brief history of the development of the Yorkshire Terrier will show that the dog was developed in the 1800’s. In England, the Waterside Terrier was often crossed with the old English terrier, a silky coated black and tan or blue and tan terrier weighing around five pounds. When crafters from Scotland came into England, they brought several “Scotch“terriers, among them the Paisley and the Clydesdale. The Paisley was a small silky coated dog in various shades of blue. The Clydesdale was a blue and tan dog with the exact color pattern as the Yorkie of today. All of these original breeds were grizzle, tan, blue, blue and tan, or black and tan. No white dog or dogs with white markings were involved in the process of developing the breed. The first Yorkshire Terriers were entered at shows as Broken Haired Scotch and Yorkshire Terriers. In the early days, dog classes were often divided by size, under five pounds and over five pounds; however, there was never a class for colors other than the blue and tan we see today.
The article states that No white dog or dogs with white markings were involved in the process of developing the breed ...
BUT
The Otter hound was used in the makeup of the Waterside terrier - Waterside terriers were used in the make up of the Yorkie according to the YTCA's Yorkie history page. Color's of the Otter hounds were not only grizzle or blue and tan in color but also piebald, chocolate and tan colored.
Otterhound Colors
The YTCA article goes on to state that
"The first Yorkshire Terriers were entered at shows as Broken Haired Scotch and Yorkshire Terriers. In the early days, dog classes were often divided by size, under five pounds and over five pounds; however, there was never a class for colors other than the blue and tan we see today" ... below is a link to the "Kennel Club Calendar and Stud book - 1874" showing classes for different colored scotch terriers, white, blue or fawn.
Kennel Club calendar & stud book - Google Books
Scotch terriers or broken haired scotch terriers were used in the make up of the yorkie; there are many early writings of blue, tan or white colored scotch terriers:
British rural sports: comprising ... - Google Books
There are additional links on my website, that direct you to other books mentioning off colored yorkies in early history or other colors of the dogs who were used in the makeup of the yorkshire terrier breed, including white skye terriers :
Links - Pine Haven Yorkies
Books also mention white Yorkshire Terriers, here's one link:
A manual of toy dogs: how to breed ... - Google Books
Some of the first prize winning yorkshire terriers were blue and tan born Yorkies.
The American book of the dog: The ... - Google Books
Unlike the YTCA and AKC who feel the Maltese was never used in the foundation stock, the Kennel Club (UK) feels that the Yorkie was a result of crosses between dogs like the black and tan terrier, the maltese and the skye terrier.
The Kennel Club
Numerous, numerous, numerous early writings also state that the maltese were used in the make up of the yorkshire terrier and that the Maltese were used to enhance the texture and length of the yorkies coat.
I have a newspaper article written in the 1960's, where a large number of members from the Skye Terrier Club of America, quit the club due to a dispute with AKC while trying to get a DQ rule for the Parti Colored coats showing up in the Skye breed (skyes being one of the dogs used in the early make up of this breed according to the UK kennel club).
Parti and other off colors have appeared in well known old time breeders and in well known show breeders lines, in addition to Nikkos, parti also has been seen in the Wildweir and Parquin kennel.
I appreciate the letter that Breezewood has posted from Joan Gordon but here is a letter from Loryn Bogren of Crownridge Yorkies, written several years ago, where she gave some insight to what she was told by AKC during the late 1990's after the Parti investigation began, as a result of her (Loryn) trying to get her parti colored Nikkos dogs registered.
"Let me know how it goes with your "off-color" club. I will help you any way I can. AKC went back as far as they could with the living dogs. They DNA'd about 42 litters. They also talked to a lot of the "old" breeders and they told them they had always been in the lines but were disposed of. Wildweir told AKC that they had more Partis than Gloria but they got "rid" of them. They didn't know the Parti color was a recessive gene and was really not gone, just not evident to the eyes. I still have their letter to me stating that the Parti color was a naturally occurring color and that they could not exclude them from the breed. Ours are NOT mixed. They are true purebred Yorkies.
Let me know what is going on. Hope you are all well and happy.
Loryn"
Written standards are a wonderful guide for trying to achieve that "perfect" goal but standards should not be taken so literally that it discriminates or casts aside healthy dogs, solely because of their nonstandard coat color due to recessive genes - these being the same non standard colors that have been documented in many early books about the breed and also surprisingly seen in the litter boxes of some of our old time and present day breeders. 125+ years ago when this breed began, coat color genetics was not understood like they are now (and believe me, there is still a lot to learn). There were also many old wives tales and untruths that led people to choose or not choose certain colors. White coats in some equine and canine breeds was thought to be inferior and weak, thus unwanted. Other than the blue born yorkies, golden, parti and chocolate colors are no more prone to health problems than the traditional steel blue and tan yorkie are - in other words, their color has not affected their health