I can't remember the one in the r32 I did but you should be able to tell the power and accessories because it's usually a heavier weight than the speaker cables.
Once you figured those ones out just use a test light to see which one is which. (ie. if test light goes on with teh car off it's the power, turn your key to ON and if the test light goes on then but goes off when you take the key out then its the accessories).
When you have the headunit working then just plug in the speakers one at a time to see which one is which.