There should be a "mark as new" option like in email. If I click on a Forum, it's possible that I'll want to come back to it at a later time. Marking it as new should reset the Forum color so I know to go back to it.
Also, when I go to a Forum with new messages, it should scroll to the earliest new chat or post as it can easily be missed if the other person typed a lot.
Customer support service by UserEcho