in the galeries/ribbon_fullsize/index.php file, you can edit the navigation:
<!-- navigation -->
<div class="nav">
<a href="#" class="first">First</a>
<a href="#" class="prev">Prev</a>
<a href="#" class="next">Next</a>
<a href="#" class="last">Last</a>
</div>
since you are using the Light design, color changes to the navigation need to be made in the galleries/ribbon_fullsize/css/light.css file.