trial and error is your friend in regard to electronics

but my bet is the white/grey speakers are rear, and the purple/green are front. Orange is usually the dimmer wire (senses lights turning on)

what you need to do is test it by getting a speaker, and using the fader/balance functions. Start by fading it to figure out front/back, and then figure out left/right from there.

usually, the wires are labeled. Pawn shops suck