Dim, but cool coloured lights? That's certainly better than bright cool ones but I still find them very annoying and overstimulating at night.
The only thing I can't do with dim, warm lighting is read small text from something other than a backlit screen. For everything else, it's perfectly fine. And if I do see myself having to do that, I'll just add a spot of light to what I'm trying to read, problem solved.
The problem is that warm lights just look dimmer than they are in reality, you need objectively much brighter warm light to see anything at all. 505nm is a commonly available wavelength that is very near the eye's peak sensitivity in the dark, so a very low powered light would provide sufficient light, and it wouldn't be more overstimulating than moonlight unless it's way too bright. The only drawback it seems to have is that it's rather close to the O-III astronomical filter, I don't know how much it matters.
I think their point is that all the wavelengths that make the lights most-useful from a safety perspective are also those which interfere with seeing the stars and whatnot.
Low pressure sodium is useful for safety (you don't need color vision to see the shadow of an attacker, a fallen branch, shiny reflective shards of a glass bottle, or a pothole), efficient (Lumen/W), and extremely tame for star-observing (look through a narrow-band filter to block the two very thin very close spectral lines (so close you need decent instruments to see that its not just a single one)).
The downside is that you don't get color vision, because the light is so close to monochromatic that you might as well think of it as truly monochromatic for human vision purposes.
Ok, but that's where I'm confused. You don't need to see everything in full colour and detail to be safe. You need to be able to make out shapes, movements and shadows.
A few years ago I lived in a neighbourhood where all the street lights had a dark yellow tint, very warm coloured. They weren't all that bright either. I could see a person a block away with ease.
Again, that was far from ideal to read a book, but why would I do that out on the streets at night?
Dim, but cool coloured lights? That's certainly better than bright cool ones but I still find them very annoying and overstimulating at night.
The only thing I can't do with dim, warm lighting is read small text from something other than a backlit screen. For everything else, it's perfectly fine. And if I do see myself having to do that, I'll just add a spot of light to what I'm trying to read, problem solved.