www.the12volt.com is a great place to get wiring info

Constant 12V+ Red/Green
Switched 12V+ Blue/Yellow
Ground Black
Illumination Red
Dimmer n/a
Front Speakers 6 1/2" Doors
Left Front (+) Yellow
Left Front (-) Blue/Red
Right Front (+) White
Right Front (-) Blue/Black
Rear Speakers 6 1/2" Rear Doors
Left Rear (+) Yellow/White
Left Rear (-) Blue/Red
Right Rear (+) White/Blue
Right Rear (-) Blue/Black

I suggest buying an adapter instead of hacking into the wiring harness. They arnt expensive and make life a lot easier. Check out the DIY section for a stereo install writeup.