My older dog Scruffy has a lot of these also. He will sometimes scratch them and they will bleed. The vet and I keep an eye on them but they don't seem to be growing very fast. If they do, I'll certainly have the vet check on them.

These warts can be white, pink or gray. Not really anything to worry about in general. Do verify this with a vet, however. Possibly an oral medication can help.