0h n0 seems to be just complex enough that sometimes you actually need to think about the problem. At least that is the case so far.
It requires a non-zero but pretty low level of "executive function", but significantly less than most logic puzzles.
In particular, a few times per game, I have to apply a little bit of "frontal-lobe" or higher-level skill to prevent myself from losing my patience for constantly applying the lower-level or "perceptual" skills required by 0hh1. In particular, I have to apply frontal-lobe skills to resist the temptation to engage in the "wishful thinking" of falsely believing I have perceived a correct next move to make.
(I engage in 0hh1.com mostly to relax or unwind, not to hone any higher-level skill.)
It seems 0h h1 has a slightly harder learning curve before the pattern recognition kicks in, while 0h n0 doesn't rely as much on pattern recognition, but is easier to learn.
There are no multiple solutions due to an unstated constraint that resolves ambiguities. I believe it is that a blue cannot be surrounded completely by reds.