Just a remainder that we still don't have proper scans of the Mario Bros backgrounds, the current ones are vector recreations with some differences when compared to the originals.
^This is true. And I suppose that the characters in Donkey Kong II were also created without a proper scan (but I could be mistaken here since they were done a long time ago). The characters in this game look a little brighter/greyish when compared to other G&W characters for some reason.