I think with most paintings like these its less about putting a naivity out there and more to do with picking out a particular energy, mood, feel, something that ran through that experience that made it feel distinct, different from the energy of their usual environments - ie. what made them decide to paint particular place and not a place 100 feet down the way. The colors, like you've addressed, are more communicative of the emotion. If it seems naive, the artist probably may know that themselves but perhaps fascinated by having an odd feeling well up in them that conflicts with their, likely by then, already cynical adult psyche, often enough they'll draw that conflict in as well.
I can't remember the artists names though but I have seen some amazing paintings of northern and eastern Africa by some of the great impressionists in galleries and they are touching, mainly in that they will use these pure and beautiful colors to almost peck out something of a spiritual feel to things (and regardless of whether one believes in that or happens to be a strict materialist - its one thing to argue against metaphysics, another to argue against a 'feel' or what kinds of emotions we tend to give saliency to that way).
What I've also found fascinating, there were other artists of the Quatro Gatos/Barcelona, it might not have been this guy, but I remember one had a really steep, something like a heroin addiction, and many of his paintings are set inside places like bars and pubs - they both have a very hollow, nagging, and emotionally desolate feel to them but at the same time the have a sparkle and shine indicating something of a paradox between emotional desolation and chemical euphoria all at the same time. Stuff like that I find absolutely fascinating just because it gives you insight into the psyche of a person that you never could have gotten out of any other medium. Music of course has that ability as well though often times its a bit more altered by the perception of the listener than visual art by the viewer.
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The loneliest part of life: it's not just that no one is on your cloud, few can even see your cloud.