Using following code you can apply two colors alternatively to the page links. just edit the colors to apply different styles.

<ul class="page_navigation">
<?php
$pages = get_pages(array('sort_column'=>'menu_order')); 
$totalpages=count($pages);
$count=0;
foreach ($pages as $pagg) {
$count++;
if($count%2!=0)
{
echo '<li class="odd">';
}
else
{
echo '<li class="even">';
}
echo '<a href="'.get_permalink($pagg->ID).'">';
echo $pagg->post_title;
echo '</a></li>';
}
?>
</ul>
<style type="text/css">
.page_navigation li.odd a
{
color:red;
}
.page_navigation li.even a
{
color:blue;
}
</style>

And if you want to display child pages of a specific page then just replace line

$pages = get_pages(array('sort_column'=>'menu_order','child_of'=>8));

change 8 with parent page id and display child pages of that parent.

and if you want to display child pages of current page then just add $post->ID instead of the page number.
like

$pages = get_pages(array('sort_column'=>'menu_order','child_of'=>$post->ID));