I think it is kind of normal for some Yorkies to change color. I don't think she should turn white though unless you bought a Biewer or a Parti Yorkie. I think they allow for small white spots on the head of a regular Yorkie but not a lot unless they are one of the other types of Yorkie.
Gracie lost a lot of her black as she matured. She has gold where a lot of the black was. |