SetPalette procedure

  DECLARATION:  SetPalette(ColorNum : Word; Color : Byte);

      PURPOSE:  Changes a single palette color

         UNIT:  Graph

      REMARKS:  Changes the ColorNum entry in the palette to the value
                specified by Color.  Values for Color range from 0 to 15,
                depending on the current mode and driver.  The changes will
                be seen immediately on the screen.

                If the value passed to SetPalette is invalid, GraphResult
                will return a value of -11 (grError) and the current palette
                will be left unchanged.

 RESTRICTIONS:  Must first be in graphics mode.