On a B&W TV you can tell whether a programme is in colour.

[Mr Blobby]

Perhaps this should be spun off into a "little things you young 'uns wouldn't know!" thread? If nothing else, might be a help for people playing / running period games...

You might also notice if it was filmed in colour or not from the dialogue. It wasn't in your face, but if being filmed in B&W the characters are more likely to make comments like 'come on, the light's green' or something. Variant of which was the old snooker narration of pointing out the colours of the various balls on the table all the time.

Sometimes you could also tell from the way the actors etc looked. My first TV in the late 90s was B&W, and on some programmes it was rather hard to read their facial expressions etc as their faces were just greyish blobs. If I recall rightly, in the pre-colour era they deliberately used makeup to accentuate the features. A variant of this could be the choices of set/attire etc not working in B&W - a prime example [I believe] being the 1960 Presidential election where Nixon's choice of suit in a TV debate looked fine in colour, but almost blended in to the background in B&W. [Not intended to be a political point, just a TV one].

However, this aspect only came up if the programme was filmed in colour without taking into account that some viewers had B&W sets. There would have been a period [for the UK, 60s/70s] in which set designers etc would have taken both types into account.