In the dashboard of a 306, you are provided with an 8-wire plastic connector (white). It has 4 pairs of wires, each wire in the pair is above and below each other:
Blue 845 and white 846...go to left door speaker.
Red 842 and yellow 841 ....go to right door speaker.
Yellow 843 and green 844 go to rear speaker (if equipped)
Blue 847 and red 84? (can't read it) go to rear spkr if equipped.
Heavier guage white wire A095 and B 085 are positive 12 volt supply wires. I THINK the difference is, one is 12 volt constant, and the other is 12 volts only when Key is on.
Heavier guage green wire # 011 # with yellow bands, is the negative ground wire.
And you will find the antenna plug-in wire, very heavy black wire with grey metal pin.