I'm on a neighborhood business committee and all the businesses in the 4 business districts do an annual "Girls' Day Out" shopping thing. Businesses are decorated in pink, everything is pink, pink, pink! The majority of women business owners in my particular district all decided to have a few strands of pink hair extensions put in the for shopping event. I brought Gracie (my Yorkie) to the business that day and we added a couple pink hair extensions to her...everyone thought it was a cute addition to the theme.
However, that being said, it wasn't the best idea because they were difficult to get out and resulted in her and my hair getting broken off - to which I was more upset about her hair than mine. So don't do heat activated hair extensions!!! lol
I can't see where a properly colored Yorkie would look all that good dyed, but as I said before...a maltese (or poodle for that matter) would look pretty neat pink I think. But yeah, as long as the products are safe.