It's funny you ask about silver yorkies. The first yorkie that I saw and made me want a yorkie was totally silver. Having never been around yorkies before I thought this was their normal color and they all were silver.
I started looking on the internet for yorkie puppies and kept seeing these little black and tan puppies......I kept wondering "where are the silver ones"
Fortunately, it was the personality more than color that made me fall in love with yorkies. Now knowing what the standard requires, I laugh at myself for my ignorance!