Which ignition wire?

I'm re-wiring a few things right now and I want to connect the 12v switched lead from the 6A box to the ignition key. I needs to be on when you turn the car over and stay on until you turn the car off. Just don't know what wire I need to connect it too. There's a yellow, black, blue coming from the column that comes from the ignition key but what one I don't know. Thanks!