My current understanding is that season 3's polyester command tunics are more green in real life than season 1+2 velour costumes, but they were dyed this way to appear to be the exact same shade of gold on screen. So the real life answer is 'they got greener' and the in-universe answer is 'they stayed gold'.
Also I know this doesn't change anything, but I couldn't resist trying to neutralise the colour of those photos from a few posts up (without adjusting the colours separately).
I started by adjusting the colour so the highlights in Shatner's eyes were grey and his collar was black, then tweaked the curves from there to make Nimoy's tunic look closer to how it appears in the show. There's obviously room for improvement, Shatner's tunic is very brown for one thing, but I think this looks a bit more natural overall.