The font color of the forum rules comes from the "page" setting in your styles and templates.
You can either change the color of the font in your page setting of your style.
Or you can change this
Code:
<div class="page" style="border:thin inset; padding:$stylevar[cellpadding]px;<if condition="!is_browser('konqueror')"> height:175px; overflow:auto</if>">
to a different class, for example to use alt1 (one of the main background/font colors of user's posts) you would change it to
Code:
<div class="alt1" style="border:thin inset; padding:$stylevar[cellpadding]px;<if condition="!is_browser('konqueror')"> height:175px; overflow:auto</if>">
You can see where I changed class="page" to class="alt1"
I would suggest changing your setting rather then changing the class though as if you are having an issue with the text being hard to read in the rules box, there is a good chance that you are having other issues on your site with visibility that you may not be aware of