You mentioned The 1967 colour series of The Avengers, which some consider as one series, since they aired in calendar, 1967, but others consider two series of production blocks which aired in early, then late 1967. The Saint also had two similar situations. Roger Moore claims he was hired by Lew Grade for a first series of 39 episodes, though the dozen that aired in 1962 are considered series one. The 3rd series of The Saint is either considered to have run September, 1964-August, 1965, or be two seperate series from 1964-65, and summer, 1965.
In the states, television programs produced for syndication often were dated by production years, not air dates. The Adventures Of Superman was ferquently called 1951-1957 (no episodes were filmed in 1952), though it aired 1952-1958.
The colour Danger Man episodes are interesting in that they may have only been produced in colour for their edited together cinema release. During season one of the TV series Branded, which was in black and white, a 3 part episode was filmed in colour and released overseas as a movie. Though it was aired in momochrome on NBC, it has subsequently aired in reruns in colour. Two 1966 episodes of the Peter Fauk series, The Trials Of O'Brian, were filmed in colour and edited together and released as a movie to theatres in Europe, though they were aired on the CBS network in black and white. NBC was broadcasting colour programming in 1965, as was CBS in 1966, so these filmed in colour episodes each could have been originally colourcasted, unlike Danger Man, which was on ATV, who didn't begin colourcasting until November, 1969.
Thanks lukegobrien for your response. I don't know if I mentioned it earlier, but the problem with UK non-BBC shows is that very rarely were ITC productions fully networked in UK - non-UK persons may find UK's commercial TV system strange, unlike US where networks show same programme across US at same time, ITV was a regional based federation of stations that could show the same TV programmes at same time across whole UK, but were not legally obliged to (and often didn't!). DVD box sets normally have the London region transmission dates - the rest of the country might not have seen them then (if at all). The colour Danger Mans are interesting because there has arisen a rumour that they were the beginning of whole colour season (S4) but season abandoned as McGoohan resigned to do The Prisoner instead. I don't believe this as the crew along with McGoohan began shooting The Prisoner immediately after these colour episodes. They were released theatrically abroad as a 95 minute film (though technically they're actually two stories linked by Japan location rather than two parts of same story - as The Saint & The Baron film releases were).
By the way, in most parts of the UK The Prisoner started transmission BEFORE the Danger Man colour episodes were shown. It is also interesting to think what the originally planned S2 of The Prisoner (No.6 escaped and now back in society tracking down the powers behind the village)would have looked and felt like!
I got hooked on the existing DVDs of UK series like Callan and Public Eye, where color episodes exist but many monochrome ones are gone. Since these earlier episodes weren't networked but aired in different regions on different dates on kinescopes (telerecordings) 16mm films transferred from tape, there should be many of these films just kicking around. Unlike tape which had value for rerecording over, these filmed copies can't be reused, but must have value being from a popular series.