stereo diagram

These colors are from a '97 Caravan but they should be the same for your car:

Gray plug, starting away from the keyway:

Pin 1 is not used
Brown / Red: LF speaker -
Dark Blue / Red: RF speaker -
Yellow / Black: tail lights (dims the display)
Orange: dash lights (tells the display how much to dim)
Red / White: 12 volts from ignition switch
Pink: 12 volts all the time (station preset memory and clock)

Black plug, starting away from keyway:

Dark Green / Red: Power antenna / remote amp
Brown / Yellow: LR speaker +
Dark Blue / White: RR speaker +
Dark Green: LF speaker +
Violet: RF speaker +
Brown / Light Blue: LR speaker -
Dark Blue / Orange: RR speaker -

Use the two plugs on the left. The big ones on the right are for the newer style plugs.