Not about to intentionally install the theme to find out if this works, but here's what I found:
http://pureinfotech.com/2015/11/28/how-remove-star-wars-theme-google-account/
Quote:
1. go to google.com/starwars.
2. Choose to change side.
3. Move your avatar to the center (between the dark side and the bright side),
4. Then click on your gmail-adress (not on change account) and then press the button to confirm that you want to restore the default settings.
_________________
“For small creatures such as we the vastness is bearable only through love.”
―Carl Sagan