stylize wp_list_pages

Hey there!
im trying to stylize the right menu here => https://www.assessortec.com/wp/?page_id=7
like this:
where the parent pages stays inside a <div> tag with background class and stuffs, aaand the subpages stays just like it is right now on lists.

the code im using:

<?php
if(!$post->post_parent){
	// will display the subpages of this top level page
	$children = wp_list_pages("title_li=&child_of=".$post->ID."&echo=0");
}else{
	// diplays only the subpages of parent level
	//$children = wp_list_pages("title_li=&child_of=".$post->post_parent."&echo=0");

	if($post->ancestors)
	{
		// now you can get the the top ID of this page
		// wp is putting the ids DESC, thats why the top level ID is the last one
		$ancestors = end($post->ancestors);
		$children = wp_list_pages("title_li=&child_of=".$ancestors."&echo=0");
		// you will always get the whole subpages list
	}
}

if ($children) { ?>
	<ul id="produtos">
		<?php echo $children; ?>
	</ul>
<?php } ?>

how to style title_li inside DIVs and &child_of= inside lists ??

thanks