Please add an exception so that viewing special/preferences/user options does not use the theme (unless of course the theme preview is chosen).
This is the standard expected feature of MW since it allows preferences to be changed should the theme have faults. Customizations to default themes eg color choices set in css should not affect the display of user options/preferences.
Classes <pre>ns-special, mw-special-Userlogin</pre> may be useful.