Tangential topics spin off of most threads and it happens on all the boards. It's human nature, it happens in face to face discussion as well. It can be frustrating, however, when you click on a thread hoping to see an update on the stated topic.
My suggestion would be to have the new discussion moved into it's own thread if it's actually a quality discussion about GT football, rather than coding the original thread. What happens when the thread gets back on topic on it's own, like what also happens all the time? Do you have to keep changing the color?