Open: portal.php
Find:
// Grab group details for legend display
if ($auth->acl_gets('a_group', 'a_groupadd', 'a_groupdel'))
{
	$sql = 'SELECT group_id, group_name, group_colour, group_type
		FROM ' . GROUPS_TABLE . '
		WHERE group_legend = 1
		ORDER BY group_name ASC';
}
else
{
	$sql = 'SELECT g.group_id, g.group_name, g.group_colour, g.group_type
		FROM ' . GROUPS_TABLE . ' g
		LEFT JOIN ' . USER_GROUP_TABLE . ' ug
			ON (
				g.group_id = ug.group_id
				AND ug.user_id = ' . $user->data['user_id'] . '
				AND ug.user_pending = 0
			)
		WHERE g.group_legend = 1
			AND (g.group_type <> ' . GROUP_HIDDEN . ' OR ug.user_id = ' . $user->data['user_id'] . ')
		ORDER BY g.group_name ASC';
}

Replace With:
$order_legend = ($config['legend_sort_groupname']) ? 'group_name' : 'group_legend';
// Grab group details for legend display
if ($auth->acl_gets('a_group', 'a_groupadd', 'a_groupdel'))
{
	$sql = 'SELECT group_id, group_name, group_colour, group_type, group_legend
		FROM ' . GROUPS_TABLE . '
		WHERE group_legend > 0
		ORDER BY ' . $order_legend . ' ASC';
}
else
{
	$sql = 'SELECT g.group_id, g.group_name, g.group_colour, g.group_type, g.group_legend
		FROM ' . GROUPS_TABLE . ' g
		LEFT JOIN ' . USER_GROUP_TABLE . ' ug
			ON (
				g.group_id = ug.group_id
				AND ug.user_id = ' . $user->data['user_id'] . '
				AND ug.user_pending = 0
			)
		WHERE g.group_legend > 0
			AND (g.group_type <> ' . GROUP_HIDDEN . ' OR ug.user_id = ' . $user->data['user_id'] . ')
		ORDER BY g.' . $order_legend . ' ASC';
}