Solarized-dark for the OLD reddit design (supports the new profile page though). Works with RES!
Obviously, subreddit styles must be turned off in the settings.
The code is a little messy because I just grabbed Reddit Slate Nights and changed the colors until I couldn’t find elements that weren’t solarized (there might still be areas that I haven’t themed, or useless bits of code – feel free to modify it).
A preview of options you can set in your extension