Copied from my post on wiring up towbar electrics...
In order on the plug.
Offside (driver)
Grey (or a strange purple - it was hard to tell) - Fog
Green/Yellow - Brake
Pink - Indicator
White - Reverse
Yellow/Red - Tail
Black - Earth
Nearside (passenger)
Unused Pin (for fog if wired)
Green/White - Brake
Green/Red - Indicator
White - Reverse
Yellow/Black - Tail
Black - Earth