Your eye is much more sensitive to green than red. Any green light will appear brighter than a red light of equal optical power, even though the red light is actually emitting more photons.

But this might not be the same with "night-vision" goggles such as those used to find these people: those sensors might be equally sensitive to red and green, or might even do better in red, especially when the higher photon flux is considered.

This might be an interesting test for Doug at some point: are red or green LEDs easier to spot with the usual night-vision search gear? Green is better for the naked eye but for a boat it might be better to assume searches at sea are only conducted with night-vision goggles.