They seem to be, but the seem to be more oily than regular darkness, only way you can easily tell if one's hiding nearby is the eyes. They have these blank white eyes, isn't half disturbing, but at least it differentiates them from The Filth back home. I nearly had a heart attack the first time I saw a Nox here.

[They are moving at a slow, but steady pace down the street now, Daniel's limp slows him down quite a lot.]