Hi I'm a newbie. I have a 2001 toyota gita had it for nearly 3 years now. We are trying to change the stereo in it as it still has the standard unit. But we are a little stuck as we dont know which wires are which as we have had a look at wire diagrams but they all have purple wires but my car has no purple wires. We have power to the new head unit we have put in it but dont know which wires are front or rear speakers neg or pos. Please help it's not nice having a car with no sounds.

oh and the car is a Japanese car.