Personally, I steer clear of the red lenses. I used to carry about a zillion flashlights when I went flying (back when I was young, impressionable, and thought everything sold by Sporty's was useful).
Now, I carry one of my many headlamps (but I bought them because I'm a mountaineer--so I NEED to own six headlamps). Personally, I'd tell most pilots to go out and buy the Black Diamond ION headlamp. It's the lightest headlamp on the market, and it's light isn't so bright that it'll blind you. It's about the size of a quarter, and it can be aimed vertically (which is very nice for reading in a bivy).
As an ex technical theater guy, I can tell you that red is useless. If we really wanted to save our vision, we'd all be using Roscolux #80 for our lenses. But red does look cool.
Dan