Had an interesting discussion with a friend once, who claimed you didn't need a torch as long as you allowed your eyes to acclimatise naturally as night fell. We got a chance to test this soon after, reaching the summit of Stob Choire nam Beith in Glen Coe just as the sun disappeared over the horizon (a common occurrence when I go ice climbing! Must speed up.). We found the descent into Coire nam Beith with the last of the light and were able to see well enough to get almost all the way down to the road before I finally gave up and put my torch on at the last outcrop across the path, which was verglassed, although my mate stuck to it and got down to the road safely. He reckoned it proved his point, although I have to say I would have been able to move a lot faster with a headtorch switched on - and he uses a head torch too(!).
Anyway, I reckon there's not much point in messing about with red or green loghts. Just make sure your batteries are in good order and use your headtorch: it's what we invented technology for.