It's just two switches with a common wire. You need to find out which one is common - probably the red. use a meter set to beep. Check which two wires give a beep when only the green button is on, and again with only the red button. Then you'll know which is common and which other wire goes with each switch. I would guess that the light switch latches on and off, and that the horn button is simple push-to-make and doesn't latch.
What do you want to do with it?