Just did a quick digi to see what it would look like. First I did it in character specific colors. Then I did it in combined mode colors.
This looks so good in the ROTF colour scheme. I hope we'll get an exclusive set of this in the future.
just to make him more rotf, maybe repaint his chestplate red, his crotch(since it is hiddenin robot and vehicle mode) and his face, his helmet gray and his eyes green
I did a second version based on the combined mode instead of the individual bots. Won't look as good in the individual modes, but looks better as RotF Devastator. Updated the first post.
In the first shot, if you made Bonecrusher more of an orange-yellow, it'd break up the yellow of the upper body. You could also darken Scrapper to a yellow/brown.