syntax theme for xcode using the dcb colors
$ git clone https://github.com/dcb-ug/xcode-syntax-theme.git
$ cd xcode-syntax-theme
$ mkdir -p ~/Library/Developer/Xcode/UserData/FontAndColorThemes/
$ cp dcb-ug.xccolortheme ~/Library/Developer/Xcode/UserData/FontAndColorThemes/dcb-ug.xccolortheme
You can also use the ThemeInstaller app from the Mac App Store. Themes are visible after Xcode is restarted.