It IS possible to change just the color of the links inside posts using CSS inheritance. For example, your forum HTML around a post is setup like this (extra stuff cut out for brevity):
HTML Code:
<div id="posts">
...
<table class="tborder" ...>
...
<tr>
<td class="alt2">
... <!-- User info here -->
</td>
<td class="alt1">
...
<div> <!-- The actual post is here --> </div>
</td>
</tr>
...
</table>
<!-- and then another table for the next post, etc -->
...
</div>
So, if you just want to change the link color in posts, this is what you add to the CSS:
HTML Code:
#posts table tr td.alt1 div a:link { color:#whatever; }
#posts table tr td.alt1 div a:visited { color:#whatever; }
#posts table tr td.alt1 div a:hover { color:#whatever; }
#posts table tr td.alt1 div a:active { color:#whatever; }
That will change the link color in posts without affecting any other link on the site.