What color is the speed dial background when an over-speed is detected?

When an over-speed is detected, the speed dial background turns yellow. This yellow color is a clear visual indicator to the train engineer that the train is exceeding the allowable speed limit. It serves as a warning that immediate attention is necessary to either reduce the train's speed or to confirm that the situation is being monitored appropriately.

The use of yellow as a cautionary signal is a commonly established practice in many operational contexts, including train controls, where it indicates that an action needs to be taken to mitigate potential safety risks. This visual cue helps ensure that engineers are constantly aware of the status of their train operation, promoting safety and adherence to regulations.