If Your main goal is to be not seen, take read. In the German army they display the visibility of white, red and green light to recruits. Red is the least visible color, human eyes are more sensitive to green, therefore the displays of night vision equipment are always in green and white.
With green light You can recognize more, therefore modern military maps are optimized for the use with green light.
But if You really don't want to be seen, use a light with a Moonlight/Firefly Mode.
The real problem with red in the real world is that it is
so hard to see with.
Most lights that flashaholics call red
are not red at all -- but are red/orange at ~630NM. The problem with 630nm is twofold: first the human eye is so insensitive to this color region that there is a propensity to make and use the lights
BRIGHTER than those of other colors. Aside from greatly increasing your IR signature this may have other negative effects on your dark adapted vision since 630nm
STILL ACTUALLY NEGATIVELY IMPACTS rod vision.
If you are diligent enough to actually seek out a light which will not negatively impact rod vision you will probably end up with something like the Rigel Systems variable light at 640nm. This color is
even much harder to see with than what most mistakenly think of as red. With both true red and orange/red there is also the
probability of increasing their output
so much (because they are so
useless to see with) that the image burned into the
cones may overpower the dim image coming from the
rods...hmmm.
At this point I will mention that this is not just an academic exercise to me. Unlike most readers of this thread I have
personally spent weeks, and weeks
and still more weeks actively avoiding looters, rogue cops and elite military units and I did so successfully by discretely employing cyan lights using the tactics I've described. Many here already know this. Others may search out those threads for nuts and bolts details.
In the real world these issues are not nearly as simple as they may seem.