While the Yorkshire Terrier breed standard describes them as having a blue and tan coat, white Yorkshire Terriers are not a separate breed. They are simply Yorkshire Terriers that happen to have a white coat color.
There are a few reasons why a Yorkie might be white:
* Albinism: This is a rare genetic condition that results in a complete lack of pigment in the coat, eyes, and skin.
* Leucism: This is another genetic condition that causes a reduction in pigment, but not a complete absence. This can result in a Yorkie with a white coat but still have some pigment in their eyes and skin.
* White markings: Some Yorkshire Terriers have white markings on their chest, feet, or face, which are considered normal within the breed standard.
It's important to note that white Yorkshire Terriers are not necessarily considered "purebred" by breed standards. However, their temperament and overall health should be similar to any other Yorkshire Terrier.
If you're considering getting a white Yorkie, be sure to do your research and find a reputable breeder who can provide you with information about the dog's health and lineage.