Bluish grey spot on dogs lip.

[Boone and Hogan]

Hello everybody, I am a new member and have a question about my dog. First off, I have a 1 year and 13 day old brittany spaniel pup named Hogan. For about 6 months now, my dog has had a little bit of a bluish grey spot on his lip (above the flews). It is on the outside of the top lip and has been getting a little bit worse. I have been trying to do some research on this topic and have found nothing, so I really hope someone can shed some light as to why this is happening, Of course, one thought was the C word, but i really doubt it. My dog has not changed at all since this discoloration of the lip. He is still the happy healthy pup he has always been.