I have to admit I have no deep knowledge of amber screens, I just thought of them because the first computer I’ve seen had one (and even now I prefer amber on black to green on black).
I think there was the thing where a green screen requires less beam energy for the same brightness, but while I can see why this might be relevant for oscilloscopes, which use electrostatic deflection (and indeed almost universally have green screens), for a large terminal screen with electromagnetic deflection it shouldn’t be that important. And besides, colour TVs existed (if perhaps not in a very affordable form) long before the 70s, so one would think that by the time of the VT100 it should have been possible to make a screen of whatever colour one wanted. Yet that is apparently not true?
I think there was the thing where a green screen requires less beam energy for the same brightness, but while I can see why this might be relevant for oscilloscopes, which use electrostatic deflection (and indeed almost universally have green screens), for a large terminal screen with electromagnetic deflection it shouldn’t be that important. And besides, colour TVs existed (if perhaps not in a very affordable form) long before the 70s, so one would think that by the time of the VT100 it should have been possible to make a screen of whatever colour one wanted. Yet that is apparently not true?