why does separating plastic from a cough drop create flashes?

It's calledTriboluminescence. Basically, when certain materials are subjected to mechanical shock, chemical bonds are asymmetrically broken. This creates a charge separation, which on recombination ionizes the nitrogen in the air.. This UV light is absorbed by oil of wintergreen crystals in wintergreen lifesavers, which then emit blue light. All this absorption-emission of light is due to electrons jumping energy levels.