I learned more about Yorkie coat color and texture from a Yorkshire Terrier breeder named Hugo Ibanez-Hornung, Estugo Kennels. One of his articles can be found on this link:
Yorky Club Magazine - United by passion for Yorkies.
You can do a search on his name to find many more articles. He has a way of describing the Yorkie coat's color and texture. He was a professor (I believe he is retired now) and he has produced over 150 champion Yorkies.
I keep one of my dogs in full coat because she does not tangle and has a beautiful coat. My male has a cotton coat. I don't want to make him miserable by always brushing out mattes so I keep him in a semi-puppy cut.