The first argument to this signal is defined to be a gpointer, but
in reality we supply a GOColor (==guin32).

Compare...

	go_combo_color_signals [COLOR_CHANGED] =
		g_signal_new ("color_changed",
			      G_OBJECT_CLASS_TYPE (gobject_class),
			      G_SIGNAL_RUN_LAST,
			      G_STRUCT_OFFSET (GOComboColorClass, color_changed),
			      NULL, NULL,
			      go__VOID__INT_BOOLEAN_BOOLEAN_BOOLEAN,
			      G_TYPE_NONE, 4, G_TYPE_POINTER,
			      G_TYPE_BOOLEAN, G_TYPE_BOOLEAN, G_TYPE_BOOLEAN);

(which can't even agree with itself about that type) and

  	g_signal_emit (cc,
		       go_combo_color_signals [COLOR_CHANGED], 0,
		       color, is_custom, by_user, is_default);

There doesn't seem to be a G_TYPE_whatever that covers guin32.