Can you tell by a pit-bulls tongue if its a pure bread?
It might be mixed with chow chow. My GSD is mixed with chow chow and has the same markings on his tongue
Have they always been there? Is your dog a mixed breed? If these spots have always been there and they are a dark almost bluish color, it may be that your dog has chow-chow mixed in its breed. Chows have dark tongues and their cross bred puppies usually have 2 color tongues.
It is common with many breeds to have a purple pigment on the tongue.