I stumbled upon this page earlier today when I was looking for the answer myself. I ended up calling Pioneer themselves and they provided me with the answer. It is as follows:
Black - Ground
Blue - Power Antenna / Control for an AMP
Orange - Constant 12 Volts
Red - 12 Volts when the ignition is on, 0 Volts when it's off
[Speakers]
[Front]
Gray - Front Right Positive
Gray Black - Front Right Negative
Green - Front Left Positive
Green Black - Front Left Negative
[Rear]
Gray Red - Right Rear Positive
Black Gray - Right Rear Negative
Green red - Left Rear Positive
Black Green - Left Rear Negative
The difference between Green Black and Black Green is Green Black is mostly green with a black stripe and Black Green is mostly black with a green stripe. If anyone finds this useful, drop me an e-mail at nacho2874@yahoo.com. Just kinda interested in how many people are installing a 10 year old tape deck into their vehicle. Peace.
Spork