I hunt a lot(nearly every night during the winter months), and I've tried everything you can imagine from plain old white lights, to red, blue, green, amber, and even black lights(dark purple). The best in my opinion is the tried, and accepted red lense for predators.
I prefer an extremely dark lense myself. I only want it to be bright enough to make their eyes shine. I use a "Marks-A-Lot" permanent marker to paint my lenses, and keep adding coats until they become dark enough. Don't use a Sharpie marker, because it'll etch the lenses, and ruin them.
The eyes of foxes, coyotes, bobcats, coons, and such shine very bright red when using a red lense. They also appear brighter with an extremely dark red lense than when using a white or other colored lense(even light red), because their eyes are just as bright, but you don't have to look for them against an illuminated background.
