Libera Ideoj is build on the works of many others.
The color scheme is based on Solarized from Ethan Schoonover, using a heavily modified derivative of the Solar template. I use the light mode for general text, and dark mode for code because us nerds do so love the dark.
The text face is Source Sans from Paul D. Hunt. I wanted a face that would stand up to large blocks of text, and while neo-grotesques are in vogue (see Roboto, San Fransisco and Segoe UI), I’m still partial to a humanist sans. The monospace font is Source Code, also from Paul D. Hunt. Mostly this choice is to keep rhythm with body text when I use inline code. Whenever feasable, I’ll be switching to Hasklig from Ian Tuomi, a fork of Source Code with ligatures designed for programming texts.
The display face is Overpass from Delve Fonts, inspired by the iconic Highway Gothic. While it’s technically a neo-grotesque, its even stroke width and bobbed terminals keep it punchy compared to the universe of Helvetica clones.
A previous incarnation used the display face Trebuchet MS, designed by Vincent Connare, best known for the most iconic typeface of the 1990s: Comic Sans. The accompanying text face was Lucida Grande by Bigelow & Holmes.