This isn't exactly about usability, but I wanted to share it with you anyway.
I've been involved in a lot of open source software projects, since about 1993. You know that I'm also the founder and coordinator of the FreeDOS Project? I started that project in 1994, to write a free version of DOS that anyone could use.
DOS is an old operating system. It runs entirely in text mode. So anyone who was a DOS user "back in the day" should remember text mode and the prevalence of white-on-blue text.
For April 1, we used a new "throwback" theme on the FreeDOS website. We rendered the site using old-style DOS colors, with a monospace DOS VGA font.
Even though the redesign was meant only for a day, I sort of loved the new design. This made me nostalgic for using the DOS console: editing text in that white-on-blue, without the "distraction" of other fonts or the glare of modern black-on-white text.
So I decided to create a new theme for gedit, based on the DOS throwback theme. Here's a screenshot of gedit editing a Bash script, and editing the XML theme file itself:
The theme uses the same sixteen color palette from DOS. You can find the explanation of why DOS has sixteen colors at the FreeDOS blog. I find the white-on-blue text to be calming, and easy on the eyes.
Of course, to make this a true callback to earlier days of computing, I used a custom font. On my computer, I used Mateusz Viste's DOSEGA font. Mateusz created this font by redrawing each glyph in Fontforge, using the original DOS CPI files as a model. I think it's really easy to read. (Download DOSEGA here: dosega.zip)
Want to create this on your own system? Here's the XML source to the theme file. Save this in ~/.local/share/gtksourceview-3.0/styles/dosedit.xml and gedit should find it as a new theme.