I remember the sistership, G-YMRU, turning up every now and then sporting its Airways Cymru colours. Must have confounded the passengers even more.
IIRC the BM livery on WLAD was not 100% identical in colour etc to the 'home' fleet. No that that's unusual, the Air Anglia livery on BM's HP Herald G-ASVO, when leased to cover a Friendship on overhaul c1975, sported a very oddly proportioned 'A' on the tail.
Matched for aspect ratio on fin of HPR-7 v F27 rather than house style?