Make Additional CSS Accessible from Admin Pages

[ Moderator note: moved to Fixing WordPress. ]

I really like the Additional CSS option that has become part of the WordPress core. However, is it possible to have the custom CSS for that option loaded on admin pages as well? I am currently using an older custom CSS plugin, and the only reason why I continue to do so is that it loads on the admin pages. This allows me to customize the look of the login page, for example, by adding a background image, or changing the font style. If I have menu options on the Dashboard that I want to hide from users who are logged in, I can add CSS to do that using my existing CSS plugin.

Thanks.