Discolored plastic- reaction to paint remover

[nachoman]

I will agree with Wayne here about the detergent/water bath. Usually, after I strip factory paint off of something, I get the same residue. I don't know what it is, but I suspect it is the effect the factory paint had on the plastic. In other words it is a demonstration on how such paint grips the plastic - by etching it slightly. I have painted over plastic like this with no ill effects whatsoever using both acrylic and floquil paints.