What I know has been done, albeit on a white leather suitcase to paint it a vibrant pink, was to scrub it a fair bit using TPS. There may be a different name for it, but basically it's used to clean paint brushes, and if you follow the directions and scrub the leather jacket with it, you should be able to paint it, possibly dye it, a different colour. Ask your hardware store, it may be called something different. You may want to try this on a scrap of leather first.