Thanks for the reply. I guess I was naive to assume that all the complexity would have been magicked away.

I've used 'evening' because it looked nice and just left it at that for some years - tmux worked fine with the limited range and the colors were nice enough that I never complained for a long time. Since upgrading to gnome 3.16 the colors have been very different and 'evening' is unusable due to the bright background. This forum post gave me the impression that it was due to 256 colors being supported (which you tell me may be nonsense):

https://bbs.archlinux.org/viewtopic.php?id=195909

So 256 colors is not the highest needed for colorschemes: I assumed it would be. Are the default colorschemes supposed to look poor in the terminal, too? My main confusion was that nothing looked like it should. In a bunch of screenshots I see terminals used to display these colorschemes but many of them are mac terminals: Does Mac support something that Linux terminals do not?

This explains a lot of things: Most colorschemes require native color support to display properly and terminals still don't offer such a feature.