Biewers and Parti color yorkies both can be tri-colored.
To be a Biewer : 1. the puppy must come from Lines that trace back to Mr Biewers dogs. 2. It must be Parti colored .
The Parti color yorkie is not a separate breed it is a Yorkshire Terrier
Some golds and chocolates can be registered Parti color only if they have the amount of white on them to be a parti color.
The AKC definition for
Parti-color :Two or more definite, well-broken colors, one of which must be white.
There are Tri color parti's, Liver Parti's and Gold Partis but they must have white.
Then there are just gold yorkies and liver color yorkies.
The same is with Biewers, only the Biewer clubs do not accept the livers and golds. So someone came up with names for their other colors separate.
The Biewer is not AKC so I guess they can call them what they want.
The gold biewers are Goldust, the Liver Biewers are Biro's and now the Cream colors are called Ocean Pearls. With the Biewer it depends what color the puppy is as to how it is registered. You can have pups from the same litter and they can be registered as separate breeds in the Biewer lines.
AKC registers all our colors as Yorkshire Terriers and are not registered as separate breeds no matter what color they are, they are all registered as Yorkshire terriers. WE use the term Parti yorkie to describe the color of dog we have. Their registration papers do not call them Parti Yorkshire Terriers. It just says Parti color in the color description area on the Papers .
In the end though, in my opinion, they are the same and are all Yorkies.