That was the reason why a family that had yorkies I looked at years ago said that that they love the yorkie breed, just as you say you love the parti color. They bred their bitch, all gold and 10 lbs, to their male, who they constantly studded out, had 7 puppies and were selling them for around $1500. Can't say i that would say they were doing anything to improve the breed.
Buyers who buy partis also like the different color, however sometimes the colors comes out on accident anyway from a breeder who is not specifically looking to get this result.
this is another questions that I've been wondering. Parti and biewer owners, how often do people ask you what breed your dog is and then when you say yorkie they ask what it's mixed with or get the "that's a yorkie?" comment. I get people asking me what Uni is mixed with bc she is so big
. I get annoyed already, can't imagine how you guys feel, or maybe it's just me. Although beautiful, i don't think partis and biewers look like yorkies, but that's just my opinion. I even look in their eyes and I don't see it, the color just throws me way off.
Oh ETA:
I did not rescue Uni, I bought her from not a reputable person. Then i found YT. I feel I am trying to right my own wrong by working with rescue. i am trying to get people to stop from making the same mistake I did.