How do I remove this dimmer light switch cover so I can paint the wall?
There are screws behind the front cover plate that hold the back cover plate to the junction box.  The front plate snaps into place.



You can see from the diagram that there should be a small indentation and a tab inside of this.  If you push the tab in gently with a flat head screwdriver, then you can just pull the front plate off exposing the screws for the back plate.