custom formatting for each <li> on wp_get_archives(); ?

For a wordpress theme I’ve designed for a friend, I require the ability to apply a seperate style to each month output by wp_get_archives(); on the sidebar. How would I go about doing this?

The HTML I’ve written for my non-wordpress hard code of the theme is like this:

<ul>
    <li class="mo01"><a href="#">January</a></li>
    <li class="mo02"><a href="#">February</a></li>
    ...
    <li class="mo12"><a href="#">December</a></li>
</ul>

each month has its own seperate ‘moXX’ class. That is how I want wordpress to output the archive links.