It is part of the BA legend that when it was returned to Aer Lingus in their livery of white and Green the lads who ferried it left a note on the flight deck which read: PLEASE FLY GREEN SIDE UP.
That's most interesting! I can confirm that I flew Copenhagen - Manchester on an Aer Lingus aeroplane probably back in the late 80s or early 90s (the memory is fading!) and visited the flight deck. On the back of the flight deck door was a sticker "Fly this aeroplane green side up"!
I remember it a round printed sticker and assumed it was common in Aer Lingus flight decks, but time plays tricks with the memory.