I've done a lot of experimenting with different colored lenses. In my opinion, the only two colors that definately help in certain situations are blue, and red. I've tried green, amber/orange, yellow, purple, and a few other odd colors over the years.
The red definately does help with predators, and the brighter(more powerfull) the beam, the darker red lense you should use. The red makes the eyes even sharper, and redder without illuminating much of the terrain that surrounds the animal. To me, it makes it less distracting. Once the animal is within 100 yards it doesn't take much light to accurately pick out the body in a scope for a well placed shot. Also, the red definately, if it's dark enough, doesn't spook a predator.
Blue is awsome, but for only one purpose, and it's not hunting. A pale blue lense will allow you to clearly see fish under water at night. It reduces the glare that normally reflects back at you when searching for fish, even in slightly choppy waters. Red, and some other colors will do this too, but they tend to make a fish blend into the bottom, where the blue makes them stand out better. None of this applies to predator hunting, but if you ever have an urge to gig fish, go with a blue light.
