What color were extinct proboscideans?

Hey guys, maybe you can help me out with this. I'm currently working on a series of paintings (If Im lucky they go to a museum) and the subject is an extinct proboscidean, so I've been thinking a lot of proboscidean skin color.
So I've been wondering, would it be far fetched to assume that extinct elephants and kin would possibly present other colors, perhaps reddish, or brown, or even perhaps (although it seems harder to imagine) blotches or patterns of other colors, maybe white? Would it look very weird to have an extinct proboscidean (not precisely an elephant in this case) have more diverse colors, maybe similar to these?:





Now, I know these animals are not related to elephants and that today, an elephant painted like this would look bizarre, but then, these animals live in habitats similar to those where ancient proboscideans lived, and there were so many species of them that I somehow don´t believe all of them were just grey, unless of course there's an actual major reason for elephants to be grey. I remember reading about how the grey skin kept a balance between the heat radiated from the body and the heat absorbed, thus helping regulate the body temperature better, but I don´t know if there are other reasons. Some say they don´t need bright colors because they are color blind, but this doesn´t seem to be the case, as I also remember reading about elephants attacking people clad in red because they associate red with Masai hunters- they don´t seem to see red the same way we do but they can´t be completely color blind either.

So my question is, do you think there's another reason why elephants are grey other than temperature control? Is there a possibility that extinct elephants or elephant-like creatures (mastodons, gomphotheres, etc) had more colorful skins? If so, what would you say the range of color would be?

PS- No pink elephant jokes, plz.

PS- This could be an equally interesting thread if we switched the elephants for sauropods which most people depicts now in bright colors...