There are also parti-colored yorkies and chocolates that are rare but do occur occasionally. There are tri-colored yorkies as well. They are usually black, white and tan and if they are from the Biewer line in Germany they are known as Biewer yorkies. If they are not from the Biewer line then they are just called parti-colored.
I own a gold and white yorkie ...she has 4 white paws and white on her chest. Her parents were both traditionally colored black and tan.
Here is a link to a thread about my yorkie Princess Chai and Mercedes, another gold puppy owned by another YT member, Julz
http://www.yorkietalk.com/forums/showthread.php?t=29342