mud stains

The black plastic bed caps had mud on them for about 7 days because I was unable to wash it because of all the weather we have had. I detailed it yesterday and notice that the splattered mud on the caps had stained them. Is there something that I can use that will remove, not cover up the stains? Thanks

Mother's Back to Black.

An APC diluted for exterior trim and a short nap microfiber. Might take a little work, but it should come off.