A lot of it was covering up mistakes. Watching TNG on a modern display, you get to notice how they didn’t match the colors on the uniforms very well. It’s particularly noticeable with the extras uniforms compared to the main cast, though even the main cast uniforms aren’t all matched, either. Mostly happens with the remade uniforms from season 3 onward.
For one example, look at Geordi and Data. I don’t think this is just a matter of lighting.
It probably didn’t get noticed much on shitty broadcast quality TV back then, but once stuff got remastered for the digital age, it all popped out.