Final answer:
The signal displayed should be red to indicate that the train must stop before proceeding onto the diverging route.
Step-by-step explanation:
When a train operator approaches an interlocking where they are scheduled to take a diverging route, the signal displayed should be Red.
The signal displays red to indicate that the train must stop before proceeding onto the diverging route. This is to ensure the safety of the train and prevent any collisions with other trains.
A red signal indicates that the train operator must come to a full stop and wait for further instructions or clearance before proceeding. Once the signal changes to a different color, such as green or yellow, it signifies that the train is allowed to proceed along the diverging route.