I was on 214 from Feb 59 to Oct 62. When I joined the sqdn, we were still doing the trials; we later became the 1st 'Operational' tanker Sqdn. I was posted out during the 'Cuban Crises'!
I was a Radar Fitter and worked on all of the Sqdn's a/c.
As for when the roundels changed to the low vis type, it was when they went into the hangar for a Minor or Major!
I cannot remember it being done by any specific date. It wasn't a significant thing in my life as it didn't interfere with the flying program.
The marking on the tailfin was unique, a combination of the Nightjar from the Sqdn crest and the Flight Refuelling Ltd logo. We were told that this was the only instance of a company trademark being used by the RAF.
I still possess my personal notebook with details of the ‘Radio Fit’ of each a/c on the Sqdn, but the shade of paint?? Sorry.