There is nothing wrong w/ your chocolate having white at the base of the hair. Some blacks will have this as well as yellows, you just can't see it in the yellows.
When you have a dog that is shedding out its coat you will be able to see it on the dark dogs but other wise it will be hidden. Mary Roslin Williams said in her book "Advanced Labrador Breeding" something like the best coat has white at the base of the hair.
