Each color represents a specific flight status:

        Gray: The flight is scheduled, but no additional status is currently available.

        Green: The flight is estimated to be on time or has arrived on time.

        Orange: The flight is estimated to be delayed or was delayed.

        Red: The flight is or was delayed by more than 45 minutes, or has been
                   canceled.

You can see examples of these colors on the airport schedule board and flight history pages.