The General Motors GM radio wire harness uses gray, orange, yellow, pink and black colors. The color scheme is generally standard for vehicles of every... The General Motors GM radio wire harness uses gray, orange, yellow, pink and black colors. The color scheme is generally standard for vehicles of every year. While the colors for standard speaker configurations differ between pre- and post-1990 vehicles, drivers will find that the scheme for GM radios has generally remained the same. If the vehicle has a power antenna, the wire is pink. The 12-volt positive battery wire is orange and is often known as the constant wire.