Here's the DW way of Orange Paint Removal.
On my rounds of local airsoft website, I've come across claims that the "Orange" tips painted on decent airsoft guns are powder coated. These "Orange" tips ARE NOT POWDER COATED (just to make that clear). These "Orange" tips are usually 2 colors/coats of automotive wet paints. First is a white base coat and on top of that would be a dayglow orange. Keep in mind though, some cheap airsoft manufacturers (STTI, Y&P, etc,) use an orange plastic for their pistol slides that are spray painted black.
Goof Off
The best/fastest results we've had is with a product called Goof Off (You want the original Goof Off that comes in a Zippo lighter fluid style can), available at most local hardware stores. This does quick work on the "Orange" tips, but is a very strong chemical. We've seen it melt cheap plastic resins used for plastic slides. Use it sparingly, in a well ventilated area, take your time and use alot of paper towels..
Finger Nail Polish Remover
This is a more gentle, slower way of removing the Orange Paint. You'll be much less likely to melt the plastic beneath, but the orange paint removal will take longer.