I would not pay extra for a chocolate, but if I was looking at a litter and one was chocolate or other color I would consider it. I am looking for Yorkies as pets only so I would not be trying to get an exotic color to breed.
My 2nd puppy I got. He was a bit of an odd color compared to the others and that is what I liked most about him. If they are trying to sell it to you as "rare and exotic" and charge you a lot extra I would pass. If it is a comparable price to the others in the litter and you like it then go for it!
__________________  It's raining Yorkies here! LOL Teek  ,Rowan  , Raksha (Grand Puppy)  , Raelyn |