Ignition Wiring

[rvanderpyl]

I am replacing my ignition switch with a starter button and two toggle switchs, one for accessories and one for the running circuits. I have pretty well figure out everything I need to make this work, but I have one red wire I cannot identify what it does.

There are three red wires, one, the thickest is the power supply, the second when attached to the power runs the fuel pump and is required to keep the car running. I have a yellow wire which is the starter and I have wired that to the starter button. There is a grey wire which supplys power to the signal lights for 'parking', and red/white for the radio. These I am attaching to the accesories toggle. The question is, what is that third red wire for? I need to know so I can decide if it has to go on accesories, or to the main power toggle.