First off, welcome to YT!
Wow, did you ever take on a controversial topic with your first post!
There are tons of very heated threads here on Parti yorkies. Try the search feature at the top of the page to search for "parti" and you will get a lot of results.
JeanieK and Pinehaven (Sue), are members here who have done a lot of research on Partis and breed them. They would likely be able to give you a lot of insight on them.
Good luck!