Black.
To access the correct wire coming from the brake pedal switch requires the removal of the lower dash and the A/C ducting that services the driver side vents. This was a fairly simple deal requiring taking out a few screws. The wire needed comes from the brake pedal switch itself, just before it disappears into a connector. After the connector the wires go into a cover and are inaccessible. There are 4 wires coming to / going from the switch. 2 blue and 2 black, so you'll need a test light to determine which one is hot constantly and which one is activated when the brake pedal is pressed. There is just barely enough wire to handle a standard blue 3M wire tap. The Prodigy controller is perfect fit and color match for the cubby-hole under the ignition key.
