How do you mean? I'm talking about if someone were to tweak the colors on their old television set on an individual basis for each game (i.e. dark and atmospheric for Super Metroid vs. saturated colors for Mario 64).
You sound like those dudes who buy an expensive TV who's almost calibrated out of the box and then declare "oh, but I want to see more RED... I'll just tweak this setting to the max", everything is connected when it comes to image, you pull a red injection here just so that looks very red and suddenly skin tones are orange.
SNES and N64 didn't have severely limited palettes so the colors on-screen are no doubt the intended ones... If they wanted to make Super Metroid darker they would - they didn't.
Calibrate range, make sure blacks are black and whites are white, as well as no black and white crush, as for tweaking it individually past messing with the brightness setting... I say don't... Unless you're calibrating your TV, then it's fine, but calibrating is not "I think this needs more blue!".
Accurate is almost always better, I mean tweaking the colors to no end is not much different than applying filters on a 2D game, of course there can be some poster childs of "it doesn't look so bad", but that doesn't change the fact that it wasn't the intended vision behind it. Accuracy can be heavily discussed though, I believe retro games are too colorfully bright without scanlines for instance:
What I mean is, of course dudes doing games in the 80's and 90's took that into account, they would pitch a brighter green than they would otherwise because they knew the TV would change it; similarly they wouldn't use a tone as dark as they would otherwise for the very same reason.
Yeah, you can compensate palette for 240p in a pretty universal way, just make it dimmer... (game by game basis would be silly, just tweak some settings and use them all across the board). But I say you're better off adding scanlines.
EDIT: Oops, double post.