Just found this:
2010 Chevrolet Cobalt Car Audio Installation Guide
Car Radio Battery Constant 12v+ Wire: Red/White
Car Radio Accessory Switched 12v+ Wire: The radio harness does not provide a switched power source. Run a wire to the steering column and use the brown wire in the ignition switch harness. Car Radio Ground Wire: Black/White
Car Radio Illumination Wire: Gray
Car Stereo Dimmer Wire: N/A
Car Stereo Power Antenna Trigger Wire: N/A
Car Stereo Amp Turn-On Trigger Wire: Pink
Car Stereo Amplifier Location: Amplifier is located behind the driver side of the dash near the firewall.
Car Audio Front Speakers Size: N/A
Car Audio Front Speakers Location: N/A
Left Front Speaker Positive Wire (+): Tan
Left Front Speaker Negative Wire (-): Dark Green
Right Front Speaker Positive Wire (+): Light Green/White
Right Front Speaker Negative Wire (-): Light Green
Car Audio Rear Speakers Size: N/A
Car Audio Rear Speakers Location: N/A
Left Rear Speaker Positive Wire (+): Brown/White
Left Rear Speaker Negative Wire (-): Brown
Right Rear Speaker Positive Wire (+): Dark Blue
Right Rear Speaker Negative Wire (-): Tan
From here:
http://www.modifiedlife.com/2010-che...llation-guide/