Sometimes I'm able to get most ball point pen off with Acetone. Or if it's on the symbol 70% alcohol. That won't remove your average flat symbol paint, even with heavy scrubbing. But if you notice the pen is kinda fuzzy on the edges, that means it's seeped into the plastic, so you'll need to sunfade it. Usually stray marks tend to come out but deliberately drawn on ones are the ones that tend to bleed in most cases I've seen sofar. n_n