You'll want to 2x Check or verify in your friend's car but according to Hayen's typical wiring is:
In Car:
Red wire - goes to stereo constant 12v (for memory)
Brown - power when ign on
Front Speaker/Left - (from radio) Sky blue/Grey+Grey/Blue
Front Speaker/Left - (in door) Red/Green+Black/White
Front Speaker/Right - (from radio) Grey/Grey+Grey/Red
Front Speaker/Right - (in door) Red/Green+Black/White
Rear Speaker/Left - (from radio) White/Blue+Black/Blue
Rear Speaker/Left - (on rear deck) White/Blue+Black/Blue
Rear Speaker/Right - (from radio) Black/Blue+White/Blue
Rear Speaker/Right - (on rear deck) Black/Blue+White/Blue
**Again Double Check as your car maybe different and I didn't install my HU, it was already in the car and I forgot how the speakers were setup. Having a multimeter helps, a lot.**
On most Head units:
Yellow - memory/clock constant 12v
Orange/White - dimmer (the swtich I think is the dimmer doesn't work in my B12, so its not hooked up)
Red - Power when ign on
Black - Ground
Amp - blue (sometimes blue/white)
Antenna remote - Blue (sometimes blue/white)
Speakers:
Left front - White/White Black
Right front - Grey/Grey Black
Left rear - Green/Green Black
Right rear - Purple/Purple Black
As far as installing Amps/Subs, look in the Audio forum.