What action is required when the order 'shift colors' is given while mooring a ship?

When the order "shift colors" is given while mooring a ship, it instructs the crew to move the National Ensign from its current position to a new location, typically from the mainmast down to the stern of the ship. This action is a ceremonial procedure that recognizes the proper places for displaying the flag when the ship is at a certain status, such as moored or anchored.

In naval customs, the National Ensign is often flown from the mainmast while the ship is underway. However, when a ship is moored or at rest, it is customary to display the flag from the stern. This shift not only adheres to traditional naval protocol but also signifies the transition of the ship from an active operation to a stationary status.

Understanding this sequence is vital for maintaining military customs and courtesies, and it reflects the respect accorded to the flag. The other options involve actions that are not directly related to the command "shift colors," making the correct action clearer in the context of maritime traditions.