I guess I’m one of the few here who uses pretty much the same approach with 4 colors as the author, with even another twist. I’m not saying I followed the same train of thought to come to this conclusion, but the names of my constants and functions are black, strings are green, and numbers are blue. The keywords and punctuation are gray to be less visible, not unlike in Python.

The added twist is a nod in the direction of people saying the white background burns their retinas, but there are more background colors than blue and white. I chose a calm light-green one, which I also use whenever I’m reading texts. It’s not exactly the combination with the most points in the scientific readability research, but I remember that the dark background lost that competition.

I attribute to these choices the fact that I notice many more typos in the code of my colleagues than they do in mine.