What signal is most effective for distress signaling during the day?

Using orange smoke as a distress signal during the day is highly effective due to its visibility against the backdrop of the sky and terrain. Orange smoke produces a bright, conspicuous color that stands out, making it easier for nearby vessels or aircraft to see and recognize the signal of distress. This method is especially beneficial because smoke can cover a wider area, allowing those looking for a distress signal to identify it from a distance.

In contrast, a bell is typically used for sound signaling and may not be effective for visual distress acknowledgment in a daytime setting. Red flares, while more effective at night, can be less visible during daylight due to their color blending with the sun's brightness. Green lights usually indicate a safe condition or a signaling of a course rather than distress, rendering them ineffective for signaling emergencies.