I found a partial solution.  When you use thottbot code that is in the format of !+<url>/T for example:

<a href='http://thottbot.com/i32254'><font color='#FF4455' tt='!+http://thottbot.com/i32254/T'>The Brutalizer</font></a>

The CSS file does not appear to be generated by the .js file or at least not very well.  You can now insert your own CSS.  Try inserting the following into your file and then change the values:

table.ttb{border-top: 3px solid #000;border-bottom: 3px solid #000;border-left: 3px solid #000;border-right: 3px solid #000;padding-top: 4px; background: #666; color: #DDB;font-family: Arial, Garamond, Helvetica;margin: 0px;text-align: left;}

and then change the values.  In the above the background: #666; will give the background a lighter gray color.

The reason this is a partial solution is that if you use the normal thottbot code that is in the format of <a href='http://thottbot.com/i32236' class='second'>Rising Tide</a> in the same file and you mouseover the item the CSS from the thottbot website will be pulled and overwrite CSS elements you modified.

Hope this helps out somewhat.

PS the rest of the CSS for the program is listed here:  http://i.thottbot.com/css/power.css as you may need it to correctly imitate the look of the standard thottbot program.