Back when I was into customizing action figures (many many years ago, really), I was accustomed to using Rit Dye to change the colors of pieces. The only drawback being you can only get darker colors. Overall it was a great way to vary what you had available to you for building. I already knew it was done for wheels, but had not thought of the idea of striping that dye into layers.
How To Dye Your Wheels (yep, the fish.)
That post leads to an admittedly silly, but illustrative video.