IMO,The above posts by Coyote Light and Boondocks are spot on. Not only is red less intrusive to predators but you can see further and better with red light. Green light is generally brighter than red however, you can actually see further and clearer with red. I can’t speak for the rest of the country but here in the east the night air has humidity that reflects the wavelength of green light. This causes your vision to be distorted when trying to focus on an object. For those of you that have access to both green and red lights, pick out a tree line about 100 yards or so away and shine the green light on the tree line then look for a dead tree with exposed branches and try counting the branches. Now switch to a red light of the same quality and count the branches. You should see that it is much clearer with red light. Also, try shining both lights at the same time in the air side by side and you should clearly see the green beam over the red beam. That is because it is reflecting off of the particles in the air that you can actually see within the beam of the green light.
I do have a lot of customers asking for green so I do offer my headlamp and gun light in green to fill the demand however, I highly recommend red over green.