The time delay courtesy light + reading lights needs 4 wires;
Grey which is switched to earth by any of the door switches (connected to 31b)
Brown connected to a permanent earth (connected to 31)
Red which is a permanent live (connected to 30)
Black which is live with the ignition on (connected to 15)
This is according to the circuit diagram and there may be numbers on the light module to indicate which terminal is which
