Black spots on my dog's fur?

My short-haired red Dachshund has always had an even coat. Now she has started to grow a black patch of hair next to her shoulder. I checked the skin under it, it is not black, its normal--just the hairs are black. I checked her fur as well and she doesn't seem to have ticks or fleas. She doesn't scratch either, and she sunbathes every once in a while. I'm thinking this is an age spot but I am not sure (she is 5 years old).