I adore the Mac OS 8 platinum theme deep down in my soul.
But I must also give a shout out to 7/8 because between Appearance Manager and Kaleidoscope, it could also look like any goddamn thing you wanted while still being more or less consistent UI-wise.
You can't do this shit on Windows without replacing the entire system shell and possibly having to give money to an abusive GamerGater. Miss me with that Stardock shit and gimme the sweet sweet @macthemes.
Interesting historical note about Appearance Manager though: Steve Jobs personally intervened to cancel it and have it removed after 8.5, and OS X is deliberately not theme capable at all. Apple was super fucking weird about Aqua and seemed convinced it was the real selling point for OSX and went out of their way to go after themes that used it for Classic or other OSes.

