Title: Get color depth (bits)
Use GetDeviceCaps function with BITSPIXEL parameter. This function returns number of adjacent color bits for each pixel.
procedure TForm1.Button1Click(Sender: TObject);
var
TempDC: HDC;
i: Integer;
begin
TempDC:=GetDC(GetDesktopWindow);
i:=GetDeviceCaps(TempDC, BITSPIXEL);
Label1.Caption:='Color schema '+IntToStr(i)+' bits';
end;