Brendan I have no idea of your Morgans fuel system where the pump might be located whether in tank or close to it.... on my 86 +8 the pump is mounted above the tank thus easy to get to. White and Purple as Richard suggests fits with my poor memory, but you will find wiring colour codes here should you have any confusion..
Wiring and Fusing - BS-AU7 Colour Codes (mgb-stuff.org.uk)
Good luck.
