Night Owl and Light Owl are Xcode themes based on themes of the same name from Sarah Drasner.
To install, create a directory at ~/Library/Developer/Xcode/UserData/FontAndColorThemes/ if it does not already exist and copy Night Owl.xccolortheme and Light Owl.xccolortheme into that directory.
Or use these Bash commands:
mkdir ~/Library/Developer/Xcode/UserData/FontAndColorThemes/
cp Night Owl.xccolortheme ~/Library/Developer/Xcode/UserData/FontAndColorThemes/
cp Light Owl.xccolortheme ~/Library/Developer/Xcode/UserData/FontAndColorThemes/
