How is the emergency stop signal indicated on the flight deck?

The emergency stop signal on the flight deck is indicated by red flares. This choice is correct because red is universally recognized as the color for danger or critical situations in aviation and maritime environments. The use of red flares quickly captures the attention of personnel on the flight deck, signaling the need for immediate cessation of operations to ensure safety.

In contrast, the other options represent different signals. Green flags typically indicate safe conditions or that operations can proceed, yellow lights often serve as caution or warning signals, and blue signs are not commonly associated with emergency stop situations. Each color and signal has its specific meaning, reinforcing the importance of using red flares as a clear and effective communication tool in emergencies on the flight deck.