No need to worry....that is 100% normal. No Yorkie starts changing color at one year. A lot of them continue to change for many years in fact. They say "Yorkies are like a box of chocolates" .... you never know what you are going to get
. They had a poll on here once and hardly ANYONE could tell the Yorkies from the Silkies. It was a TOUGH poll and your question is a normal one.