I guess it depends what you want to use them for.
I have green and blue glowrings, just because those happened to be the only available colors when I bought them ; good to attach to anything you need to find in the dark. A red one might be a more attracting color, when looking for those damned car keys, lost somewhere in the grass.
I use Krill lights too.
I recommend the Extreme models for more light (and still a good 50 hours life on a pair of batteries). I use them with easy-to-find AA sized lithium batteries, for long storage, inside the rucksack and in the car kit. I also keep one in my main suit-case, which I use a few times around the year.
As indicated on their web site (
http://www.kriana.com/), green is the brightest colour, then blue then white.
I get a white Extreme 180 for reading maps, without altering colors.
A 360 orange or red is good for signaling (whirling, attached at the end of a yard long laniard). I reckon a green one would be a bit brighter, but red and orange spell EMERGENCY to everyone.
Alain