[Boofo]

Ok, here's the full code. Sorry I didn't do this the first time.
In the threadbit template

Find:

   <a href="showthread.php?$session[sessionurl]t=$thread[threadid]$thread[highlight]"><if condition="$show['gotonewpost']"><strong>$thread[threadtitle]</strong><else />$thread[threadtitle]</if></a>

REPLACE it with:

   <a href="showthread.php?$session[sessionurl]t=$thread[threadid]$thread[highlight]"><if condition="$show['gotonewpost']"><strong><if condition="$thread[forumid] == xx"><font color="red">$thread[threadtitle]</font>
<else />$thread[threadtitle]</if></strong><else />$thread[threadtitle]</if></a>

Remember to replace xx with the forumid of the forum you want to do this in.