Xcode > Preferences > Fonts & Colors > Plus Button > Duplicate Theme > Name The New Theme > Update The New Scheme > Close Preferences > Coffee & Code > Kill Xcode > Launch Xcode > Preferences > Fonts & Colors > New Theme Missing!?!
Xcode Version 9.2 (9C40b)
I could duplicate the xccolortheme file without a problem. The issue was permissions. It had the wrong permissions! What the deuce!