SetBkColor procedure

  DECLARATION:  SetBkColor(Color : Word);

      PURPOSE:  Sets the current background color using the palette

         UNIT:  Graph

      REMARKS:  Background color values may range from 0 to 15, depending on
                the current graphics driver and mode.  On CGA, SetBkColor
                sets the flood overscan color.

                Using the colors in the palette, SetBkColor(N) sets the
                background color to the Nth color in the palette.  A call
                to SetBkColor(0) always sets the background to black.

 RESTRICTIONS:  Must first be in graphics mode.