I’m playing Devil’s advocate here, but…
Well. We’re not schools so what the local comprehensive gets up to doesn’t really matter.
We can still have inter-flight competition on our squadrons. It doesn’t require coloured additions to the uniform.
We’re dealing with flights of a dozen cadets or so; not a stream of couple of hundred, where the RAF might consider the use of coloured identifiers necessary.
There are plenty of oddities out there… Some squadrons seem to have an unnecessary desire to introduce all sorts of weird stuff.
It just seems to me that coloured flight tabs fits right in with dressing duty personnel in red British Army SNCO sashes, special “NCO only dress regulations” like wearing stable belts outside the jersey, and giving the OC a “symbolic whistle” as a badge of office.