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;