If you add the rule I mentioned to the bottom of your stylesheet, it will just change the subcategory names link color.
The problem with what you're doing here:
a:link, #navEZPagesTOC ul li a {
color: #000000;
text-align: center;
text-decoration: none;
is that the part in red tells the browser to change all links on the site to that color. If you just want to change the EZpage table of contents text color, you'll need to separate that into its own rule, but it doesn't sound like that's what you want to do.
To find out what you want to change and where it is in the stylesheet, install the Firefox browser and the Web Developer plugin for Firefox. You can use those to see where in the stylesheet you change the styling of the various page elements.
Ctrl-Shift-Y will allow you to hover over a section of the page and see the class and id names for that section in the box at the top. The statements in the stylesheet that begin with # are id's and the ones that begin with dots are classes.
Ctrl-Shift-E will open the CSS editor and allow you to edit the stylesheet and see the changes in real time without changing anything permanently. An essential tool.
Some prefer Firebug, which does much the same thing.
(If you're using Firefox 4-8, you'll need to remap the editor shortcut, since Firefox has appropriated Ctrl-Shift-E for an internal function - I use Ctrl-Shift-Q.)