When you open forum home, the jeep logo is brown instead of grey if there are new posts. If you view the forum, there is an orange 'new' tag next to each updated/unread posts in a topic.
You can also hit on the 'Unread' button at the top of the site above the menu bar.
But, I will take a look into seeing if I can make the topic subject bold on the forum view, so it's a little more defined.