Just the ability to click a button or (better) move a slider to change the background of the editing area, not just the preview area. Would be a boon for these eyes, as I design mostly in the evening.
You can invert the whole screen with a setting in the accessibility system preferences. The default shortcut is Ctrl-Opt-Cmd-8.
Another option to consider: https://justgetflux.com
It can adjust the color temperature based on the time of day, automatically. Of course, that means colors may seem different at night.
I use Flux for some time now. It’s so great that Apple borrowed the idea and included it in iOS 9.3.