Thanks mashby.

So if I was goona change the color of the "welcome to our newest member, **** bit in the forumhome template,
the **** representing the link of the members name, I would change:

Welcome to our newest member, <a href="member.php?s=$session[sessionhash]&action=getinfo&userid=$newuserid">$newusername </a>
</smallfont></td>

To:

Welcome to our newest member, <a class="new" href="member.php?s=$session[sessionhash]&action=getinfo&userid=$newuserid">$newusername </a>
</smallfont></td>

Am I right?

Yes, that should work. :)