[Lynne]

Look at your source code for that page. In it, you'll see something like this (this is from 3.7 beta 2, yours may be slightly differerent):

<pre class="alt2" dir="ltr" style="
		margin: 0px;
		padding: 6px;
		border: 1px inset;
		width: 640px;
		height: 34px;
		text-align: left;
		overflow: auto"><span style="color:#000080">&lt;b&gt;</span><span style="color:#000080">&lt;font size=<span style="color:#0000FF">

The blue is defined at the beginning with that span tag. Do a global search through your files for "000080" and it comes up a couple of times including in file class_bbcode.php around line 2130. I think that is where you need to change it.