It certainly was unofficial. It was only the NI Flight a/c that were "modded".
You may find that the BATUS a/c was either on its major servicing or had been bent, and a NI a/c was covering for it.
Of course the Boss knew the number of the a/c he was to take, however, it was much easier for him to walk to the one with the yellow, red, blue or whatever coloured nose!
No, he didn't necessarily have the red one, he just took what was given to him by us reems. To a certain degree anyway.
We were a very small flight. Probably no more that 25-30 guys from the boss down. 5 a/c, with usually one away on major servicing. Plenty of totally unofficial things went on, "the fish runs" to The Mull of Kintyre, hunting for the Loch Ness Monster, and plenty of other trips. But, we also worked bl**dy hard, and carried out our duties to he best of our abilities.
Happy days!
BM