SETCOLOR GuiFile ColorNumber R G B

This command allows you to change the color of a screen.

GuiFile         Is the Gui4Cli file who is, or will, open on the
                screen whose color you want to change.

ColorNumber     The number of the color you want to change.
                The first color (the background) is 0.

R G B           3 numbers, ranging from 0 to 15, specifying the
                values for Red, Green and Blue respectively.

Ex :
SetColor  MyGui 0 10 8 8

- will set the background of the screen that MyGui is (or will) open
  on, to a yukky brownish color.