Maybe some bizarre stage of gray would look like that for a bit, but it wouldn't be permanent. Or maybe an Appaloosa that's varnished strangely. The closest you'd get is a very pale buckskin.
This is really interesting. My sister's horse is an Arab x Lipizzaner, and he has always been grey with a black mane and tail and dark legs. I always called him a grey, and that's what he is on his passport, although he's most likely strictly a blue roan or something, right?
Pics are from our last cross country, so pretty recent - and he has always been this colour in the four years we've known him, and as far as I'm aware he's not a dapple grey gone light. He's 13 or 14 now.
He is grey. Eventually, he will be completely white, in theory. Old age can beat the greying process in some horses. The mane, tail and legs are often the last to retain colour, so it is not usual to see them dark for an extended period of time. Have you compared pictures of him now to when you first bought him home? I would be interested to see older pictures
Yep, like others have said, just a particular shade of buckskin that is known as "buttermilk". Genetically (as much as we currently know about genetics, anyway) no different than any other buckskin out there.
As for the frosting, pretty much any buckskin horse can have frosting. I'm not sure whether there is any connection, but IME, it does seem to be more common or more apparent on the lighter colored buckskin horses. I don't recall having seen very many that were a rich gold color that had much frosting.
Buttermilks are slightly more unique than your average golden buckskin though. I prefer the darker shades, but I can see the draw to the lighter ones as well. It's fairly common for their points to be more of a dark chocolate brown as well instead of a stark black.