How can I edit the background color of "save game" -dialog box? What about "restore game" -dialog box?
The default color is grey but I'd like to use rather orange.
You will have to create your own GUI for that. Look around for GUI tutorials, they should help you.
Here are some very good tutorials for GUIs:
http://www.sylpher.com/tuts.html
There are 3. Just do them in order.
You can try this, too:
http://gac.gamespage.com and look for save\load tutorials in the Tutorials page.