If you have purchased a brand new car stereo and wish to install the stereo on your own, then you will need to know where the red, yellow, and black stereo wire colors go when attaching them to the stereo. The stereo wire colors include blue, white, purple, grey and orange. The red wire is for the 12 volt ignition, which can be attached to the stereo. The yellow wire is the 12 volt battery wire, which should also be attached to the stereo for power. The final wire, the black wire, is the ground wire. This wire, once attached to the stereo, will help ground it.
For more info, see Car Stereo Installation: A How To Guide