Thanks for the feedback everyone

I used isopropyl (rubbing alcohol from Bunnings) to remove Wheeljack's coloured stripes. Alas it also removed the white paint from the roof and I had to repaint it. It's because the entire roof piece is transparent plastic painted white, then painted red/green. There's no such problems with the body because it's cast in white plastic.

I also have trouble with white paint and if you look closely you can see streaking/clumping on the roof . You can't see it in the photos but in real life you can also see it's a slightly different shade. I'm going to try it again later.