Some animals, especially varmints and predators, can learn to associate white light with humans which might make them run off as soon as they spot the beam. Since red lights aren’t all that common, these will surprise the animals. Some species, especially canines find the red spectrum difficult to see, allowing the hunter to get close enough for a shot.
Also, most predator’s eyes glow in the dark, and red light arguably makes this reflection easier to see from longer distances, up to twice as far as the furthest area the beam itself can reach. There’s a debate on what color of light works well for which species.