Tom,
Before you resort to dyeing the top,.......try useing 3M's general purpose adhesive remover, I use it to "strip" my top of road grunge, esp, after a few hours driving on the road in the rain,....the white top takes a beat'in.......clean a small area at a time, use plenty of WHITE rags only,,,,,NO COLORS!.....stuff is pretty good at "stripping" up crap out of the grain, don't stay in one area too long, clean with strokes following the grain, not against,,,,,,I have a white interior as well, so I know what a BEOTCH it is to clean tuff stains.....regardless of where you might use the 3M cleaner, always test FIRST,.....cause it will strip!......keep it off paint!........and NO silicone vinyl protectorants on white, soap and water, keep clean,,,,,don't let it go to long!