I've been searching all over the forums for a way to do this, and the closest I've come to so far is Here. The problem with that is it only changes the theme for 1 page whereas I need it to change for the whole site. What I've done is made 5 copies of a theme and just changed the color scheme of each. I would really appreciate if someone could help me find a way to allow admins to change the theme without having to change the _config.php file.
Thanks in advance,