The wire colors are Red, White Black and Brown, Red is + 12 volts Black is - 12 Volts White is a common color for GM interior lights, and brown is a color they use for the brake lights.
I had a 1986 Camaro that came with a rear window power pull down, because people were slamming the back window and breaking it.
its most likely an option your car did not come with.
I would bet your gas gauge does not work because the tank sending unit needs to be replaced, that is the common cause of gas gauges not working. one thing you could try is to disconnect the ground wire to the sending unit and see if the gauge moves to past full. better yet if you have a multi meter you can test the sending unit Ohms without removing it.