I don't know how much access you have to the underlying code, but I think you can edit your templates through your Blog Admin. The bit that applies to Recent Comments is this:

{{if blog.recent_comments}} <div class="component"> <div class="componentHead">Recent Comments</div> <div class="componentContent"> <div class="componentRecentComments"> {{loop name=blog.recent_comments limit=5}} <div class="componentRecentCommentsItem"> <a href="{{permalink_url}}">{{if title}}{{title}}{{else}}Untitled{{/if}}</a> </div> {{/loop}} </div> <!-- componetRecentComments --> </div> <!-- componentContent --> </div> <!-- component --> {{/if}} <!-- blog.recent_comments -->

Everything I've read says "up to 5 recent comments can be displayed" but you MIGHT be able to up that by changing the number in the template. Colour is much easier: go to the Control Panel, select Look and Feel, select "colors" and choose a template (I suspect you already know this!) but here is an article on fully customising your colour scheme.