1989 Grand Prix wiring diagram

I have a 1989 Pontiac Grand Prix with ungrounded speakers.  Could somebody please tell me what this means?  It has a seperate radio and tape player and the gm harness for that year doesn't fit it.  I cannot seem to find the speakers with my tester and the wires connected to them do not match whats going to the radio.  Could somebody please hook me up with a wiring diagram or give me the down low on what i need to do to get my reciever hooked up.  I greatley appreciate it.

1988-91 Pontiac Grand Prix Stereo Information Constant 12V+ Orange Switched 12V+ Yellow Ground Black Illumination Gray Dimmer Brown Antenna Trigger Pink Antenna Right Rear Front Speakers 4" x 6" Dash Left Front (+) Tan Left Front (-) Gray Right Front (+) Light Green Right Front (-) Dark Green Rear Speakers 6" x 9" Rear Deck Left Rear (+) Brown Left Rear (-) Yellow Right Rear (+) Dark Blue Right Rear (-) Light Blue