Why are my malamutes elbows red?

I have a 3 year old Alaskan malamute. A year and a half ago, her elbows started to color red. She does like to sleep on a hard surface and that shows (the hair on the elbows is thinner), but to me that does not explain the coloring of the otherwise almost white hair of her front legs' elbows. My vet is clueless. She checked and there is no bacterial infection, so her idea was, that the coloring occurred because of the beta carotene in the food. After a year on a beta-carotene free diet, the size of the colored area has decreased, but only marginally. So, I cannot be sure that the dog’s diet had anything to do with this. It could also be that the colored area has decreased because I have been applying an ointment (basically glycerin) almost daily. My dog is otherwise healthy and full of energy and her elbows do not seem to cause any pain.Has anybody encountered something like that with their dog(s) and has a solution?