SetDAC ( nColor, rVal, gVal, bVal ) -> lvalid 

   Sets the VGA-ColorCodes for nColor (0-15) to the passed
   Red-, Green-, Blue-Mixture (Values 0-64)

   PARAMETERS:
   nColor      0=Black ,  1=Blue ...
   rVal        RedPart
   gVal        GreenPart
   bVal        BluePart

   RETURN VALUES:
   Colors could be set ( .t. / .f. )

   EXAMPLE:
   SetDAC(C_RB,25,17,23)              // Magenta gets Brown/Red
   SetDAC(C_RG, 41, 31, 24)           // Brown gets darker
   SetDAC(C_HW,55,55,55)              // White gets darker

   Have a look at Demo.prg's function VgaMenu(), in there SetDAC
   is used very heavily.