It depends if there are any loose wires coming out of the car from the phone kit its self. if there is more than one wire, it will depend what make of phone kit it is as to what colour of wire you need to connect the wire from the stereo to. If it is an Autoleads kit the mute wire should be blue, Parrot kit can be blue white or yellow depending on kit, motorola kit is green, prowave is usually pink or brown. If it is ant other kit im not sure, so it realy does depend on the make and exactly what spare wires you have coming from the car if any. Hope this might help!