Aftermarket power antenna wiring help

[P8riot0366]

I'm in the process of replacing mine with a "Metra" power antenna that has three wires: Ground (black), 12v (red), and switch (blue). I just can't figure out which one goes to the grey wire (antenna up) and which one goes to the white wire (antenna down), so that I can solder the wires to the stock connector.

I know that the black goes to the green wire, but that's it. Anyone know?

I would test it in the car, but I am in the middle of replacing the engine wiring harness and don't have the battery connected.