Which color signal is used to denote distress at sea?

The correct choice for signaling distress at sea is red smoke. This color is universally recognized as an indicator of emergency and distress. When red smoke is deployed, it creates a visible alert that can be seen from significant distances, whether by aircraft or nearby vessels.

Red is commonly associated with danger and urgency, making it an effective color for distress signals. Such signals are crucial in maritime situations, where visibility and immediate recognition can save lives.

In contrast, blue smoke, orange smoke, and green smoke do not have established meanings in maritime distress communication and may not alert rescuers effectively. Thus, red smoke stands out as the standard signaling method for expressing a call for help in emergency situations at sea.