Syntax highlighting based on the colour palettes of Radiohead’s album covers, designed with readability/navigability in mind, and covering the whole bright-to-dark spectrum to cater for all lighting conditions.
Clone repo:
$ git clone https://github.com/jeevn/rh-xcode
Move theme files:
$ cd rh-xcode/themes
$ mv *.dvtcolortheme ~/Library/Developer/Xcode/UserData/FontAndColorThemes/
Now relaunch Xcode, the themes should appear in Preferences.