To change the background color from the default grey color (RGB 0x99 0x99 0x99) to something else, you may modify the associated .rtm file with your .dsn file. You may modify the .rtm file with any text editor. Notepad works well. The line you need to modify will look like this:
The '#' indicates hexadecimal.
The first 99 indicates the red channel (00-ff)
The second 99 indicates the green channel (00-ff)
The third 99 indicates the blue channel (00-ff)