Colm
Any debate on UTA green can, happily, be definitively settled as numerous examples of actual paint exist. The most accessible is on both the "red-hand roundel" and the post-1963 "coast of arms" UTA crests in Selwyn Johnston's "Headhunters" museum in Enniskillen - the background boards in most crests in that collection are actual paint from the companies concerned. Prior to installation in Headhunters they were deliberately kept in a location away from sunlight to preserve colours.
If anyone is interested in some of the more obscure, or least verifiable, actual liveries of the past, that collection is an ideal source of reference. DUTC / CIE dark green (same thing, as CIE copied it!) can be had there too on the backgrounds of the DUTC crest and Flying Snail.
The only thing to be aware of is that colours don't translate well from actual to model, or worse still, vice versa; 461's current green is a case in point as it is not accurate CIE green, having been copied from the late Drew Donaldson's models.
Accurate UTA green may also be found on some preserved buses. Just as CIE copied DUTC green, so did the UTA copy the old N I Road Transport Board's green, though they inverted the light and dark on buses.
For the record, NCC, LMS and (post 1935) GSR maroon were the same. There is some evidence that the BCDR may have used the same stuff from time to time, but in any event their own maroon wasn't much different - maybe a very slight shade darker, son made indistinguishable by brake dust and wear 'n' tear!
Having seen your models years ago at an exhibition, they certainly look the part to me - excellent work too, most inspirational. If there is some slight in discrepancy it's such a miniscule one as to be unnoticeable.