Sorry to bring back an old thread, but just tried colorX myself. My folks have a camper that sat outside all winter (it's entire life actually) and had black marks all down the sides. They hit it with all of the standard cleaners (even the stronger citrus based household cleaners) to no avail. Greased lightning would take it off, but we all know what it would look like afterward.
I tried some 3m SMR by hand and it came right off and left a pretty good shine. I didn't want to have to do the entire thing (huge) and then wax it all again, so I thought colorX would be the trick. To my surprise, either by hand with a folded terry or by PC @ 6, it wouldn't even touch it. The SMR by PC removed it instantly. Now I know it was the abrasiveness of the SMR that provided the cleaning action, but I was hoping the chemical cleaning ability of colorX could do the trick. I have some AIO, but haven't tried it yet (until just now, I thought colorX was supposed to be stronger). I will try the AIO to see if it works any better. Do my results seem inline with everyone elses? Was I just using the wrong product?
VV