This isn't regular colourblindness to begin with, so there's no real measurements we can use.
However, if you go into an art program and take a night scenery picture of a forest and turn it black and white, you'll see how that can easily affect a characters orientation. Plus, his sight might be further altered due to things we are not aware yet.
Either way, his vision at night is not making naviagtion easy as he couldn't even distinguish the slightest shine of light at the sky, to tell where there are streetlights or such and hence go find a pathway.
That's interesting! Thanks!
I don't have color-blindness myself, but I don't think the night affects someone with color-blindness the way this manhwa makes it out to be? I think I read somewhere that someone with color-blindness tend to have better night vision if anything... granted when I say color-blindness, it's usually the case of not being able to perceive certain colors instead of the entire range, but in theory, this should differ in terms of night vision. Also, the first 2 chapters make the MC out to be a bit on the annoying side at the moment.