function GetNumColors: LongInt;  
var  
   BPP: Integer;  
   DC: HDC;  
begin  
   DC := CreateDC('DISPLAY', nil, nil, nil);  
   if DC <> 0 then begin  
      try  
                BPP := GetDeviceCaps(DC, BITPIXEL) * GetDeviceCaps(DC, PLANES);  
      finally  
         DeleteDC(DC);  
      end;  
      case BPP of  
         1: Result := 2;  
         4: Result := 16;  
         8: Result := 256;  
         15: Result := 32768;  
         16: Result := 65536;  
         24: Result := 16777216;  
      end;  
   end else  
      Result := 0;  
end;