From experiments using optical light for communications links, red light certainly suffers less attenuation by the atmosphere at ground levels.
Though given that many head torches have a strobe setting, then that would be a choice as you have it with you anyway. (Even if you forgot about it, as I did on a survival course.)
But, if you have a red filter (as opposed to a red LED), then I'd suggest using the pure white light. As you are using your batteries to generate the power across the spectrum, so filtering some out is just wasting resource.
I would expect that and regularly flashing light, of any colour is going to be effective at night. And the regularity would make it stand out from the random flashed of people using torches to see by.
General carried to be found:
The knowledge that you have stuck to the route plan you left with someone back home. And you are going to be missed.
(Apologies if someone has already had that one....)
Being very pedantic, though it does not have a huge bearing on this topic....
Natural white light is usually full spectrum, but what we perceive as white, may be quite different. White LED/florescent lamps will put out a mix of red/green/blue, that we will see as white. Look at one through a prism (usually this is the bottom of a beer glass, when having this discussion) and you should see distinct colour lines. Incandescent lamps do produce more of a continuous spectrum.
Jules