Looks like he is trying hard to get flat and blend in. I think maybe he is quite young. From what I’ve seen that strong red tone tends to fade as they get older.
@bjywamer Hi Barb- no, actually grey squirrels usually have grey tails, maybe with some red but nothing like this. However, Joanne just commented that from her experience, "that strong red tone tends to fade as they get older," so she thinks this must be a young squirrel. (New information for me today :-)