Do dogs have 'liver spots' on their skin?

[PetFriendly]

I have a little Pom/Shih Tzu mix who is just over a year old. He is white with tan spots. The skin is pink where there's white fur and beige-ish where there's tan fur. how ever on his underside (furry or not) he has what look like liver spots, and white hair grows over them. They used to be just where there isn't much fur but have since spread to most of his underside and are now moving up his rib cage behind his front legs

Anyone know what the spots are and if they are cause for concern?