I am a model railroader and have been using this technique for a few years now. I made up a one ounce jar of this stuff using Testors liquid cement as the solvent back in 2005, and I'm using the same jar today! I mixed several different sprue shavings with no adverse effects or reaction (the were all the same type of plastic), and the overall color was gray.
They only disclaimer I must give is that if you have a fairly large or deep hole to patch, you'll have to let it cure for a few days so that the solvent has a chance to evaporate all the way out of the plastic. Be dissolving the plastic i