Do you have examples of a color scheme which would work better, or other suggestions on how we could improve it? I'm thinking the ability to customize color schemes would be a useful feature to add.
Not really actually, I was going to recommend Solarized[1] and base16[2] but both fail to pass AAA according to WAVE[3]. I'd recommend installing the WAVE extension for Chrome or Firefox as a start point.
[1] http://ethanschoonover.com/solarized/ [2] http://chriskempson.github.io/base16/ [3] http://wave.webaim.org/