Trying to decode the FSM is driving me frikkin bonkers. I've searched my nuts off but none of the data is for my model year. I'm hoping I can appeal to you all and you'll tell me what color of wires to look for under the dash. The car is a 2005 Impreza RS.
Here's what I think I found out, but I have VERY little confidence that I'm right:
Horn: It looks like to get the horn right, I need to supply 12V to the + side of the relay, then connect the ground side of the relay to the Red-Green wire before it goes into the horn switch.
Parking lights: To switch a relay off the parking light switch in the control stalk, it looks like I need to connect the Black-Red wire exiting the switch to the + terminal of the relay and then ground the other side.
High Beams: To switch a relay off the high beams, it looks like I need to connect 12V to the + terminal of the relay, then connect the ground side of the relay to Red-Black wire before it enters the control stalk.
Man, this is one messed up wiring system. Why are the Horn and High Beams ground switched while the parking lights are positive-switched? Why doesn't the high-beam relay control the high beams? Argggghhh!