Do you have an example of a truly exotic programming concept? I'm really interested in weird PL stuff.
I'd also look at Unison, for a more recent exotic programming language concept.
And what GraalVM is doing with the polyglot layer is quite interesting.
Finally my recent favourite is PPL, probabilistic programming languages.
And for more I'd recommend this podcast https://futureofcoding.org/episodes/
Cellular automaton is vastly popular as a concrete mechanism for rule-based programming (PuzzleScript being a good example), reversible computing is no longer interesting because of quantum computers and perhaps homomorphic encryption, probablistic programming is a large enough niche that it was never exotic, circuitry-based declarative programming is not even a niche (cf. HDLs), self-modification as a single control mechanism has been tried multiple times throughout the history (often combined with string rewriting paradigm, which itself has been even more popular than self-modification), ... The list goes on and on.
Probably the most exotic concept that I have ever seen is a multi-dimensional control flow (most famously Befunge [1], with some other lesser-known precedents), but there has been several programming games making use of that. Gravity-based programming [2] and the Infinity Machine [3] might be interesting if you allow hypothetical ideas.
[1] https://esolangs.org/wiki/Befunge
[2] https://esolangs.org/wiki/Gravity
[3] https://www.chiark.greenend.org.uk/~sgtatham/infinity.html
https://en.m.wikipedia.org/wiki/Icon_(programming_language)
Also maybe Self and Joy (IIRC).
I like John Tromp's Binary Lambda Calculus and Binary Combinatory Logic[2]
[1] https://esolangs.org/wiki/Language_list [2] https://tromp.github.io/cl/cl.html
https://esolangs.org/wiki/Piet
Programming as an abstract painting
Some people write write-only code in perl or in K.
Others using category theory and Monads.
Not sure if abstract colors are any worse.
In practice I doubt there is a significant difference. It's all incomprehensible for the normal coder.
At least in theory you could imagine using new parts of your brain with colorful programming. Kind of analogous to Richard Feynman picturing physical concepts using textures.
There is color forth as an practical attempt to program with the help of colors.
Esoteric languages like Piet, they aren't solving a problem. They are just being obscure for the sake of being obscure. This isn't interesting, and it doesn't really teach you anything of value.