$my_graph->set(
  x_label        => 'X-Label',
  y_label        => 'Y-Label',
  title          => 'Title',
  do_stats       => 0,
  symbolc        => 'black',
  y_min_value    => -150,
  y_max_value    => 200,
  transparent    => 0,  # << add
);