Ford Repair Questions? Ask a Mechanic for Answers ASAP
The best way to find which wire it is would be to put the vehicle into reverse with the ignition on and put a multi meter to the lamp connector to check which terminal has voltage. You will know which wire it is then.
We could tell you the colour as per the diagram however colours are often wrong so you could be led up the garden path looking for the wrong colour!
I have already told you put the vehicle into reverse and use a multi meter on the connector to determine which wire it is. The wiring diagrams although showing colours are more often than not the wrong colour so it will not help you at all!