Do you mean the user UI themes that you can select as a user from the Cog icon on the user side? the same
you can set the default user ui theme by setting:
admin->theme manager ->Themes settings then
Default User JS UI Theme:
If you mean colors with these theme, you can customize these these as you like, these themes files in the
folder js/themes
You can remove any themes that you do not like or customize them also
Thanks
Mewsoft Support www.mewsoft.com