I need to know how to hook up a head unit in a 98 chevy lumina i dont understand the wiring in the car

The colors are as follows. grey/tan+ LF, green/ lt.green+ RF, brown+/yellow LR, dk. blue+/blue RR. You can also verify the speakers by using a 9v battery. Hold one wire on one terminal of the 9v battery then just strike the other wire for only a second DO NOT HOLD the wires to the battery for more than an instant. You will hear a pop noise from the speaker.
Orange is memory, yellow 12v switched, black ground/earth.

***Warning!!!!!! There's 2 yellow and 2 grey wires (other grey is dimmer). If the original factory harness is still there and not cut up, all the speakers will be next to each other on the plug(s). If not, you MUST test the wire(s) with a test light (or some other way), verify the 12 switched (yellow) incase a fuse is blown. Same with the dimmer lead, you need to turn up and down the dash dimmer to get a response from that wire. If you use the wrong wires you will send 12V into the speaker leads from the radio and kill the radio!