Don't you think when the rust shows in the trees they are at their most beautiful? But have you ever tried to find a rust leaf on the tree? Some years I go out and pick up leaves with good color in them. When I bring them home, I dip them in wax. Then they can stay for an extended period of time after they are dipped.
But I have never, ever been able to find a rust leaf. When I get to the trees that are "rust" I see some green, yellow-green, yellow, redish-yellow , dark red, and various shades of brown. Basically every color except rust. From a distance the spackling of the colors above give the illusion of rust. Or if you are standing close enough to see all the colors in details just cross your eyes. You'll see rust there too!