I have my "rule of three." Pick any three colors and use them together (my foyer is brass, evergreen-ish, and mint) - they work visually for everyone I've met. Pick any three musical notes, even on a microtonal scale, and they form a pleasing chord. Any three simple flavors (chocolate, dill, and cayenne?) may be weird but interesting but not overwhelming.
This echoes the rule of three from Latin rhetoric. https://en.wikipedia.org/wiki/Rule_of_three_(writing)
With any three things, you have harmony to humans. More than three and it's iffy. Again, I'm not an artist (so I stick with threes!).
Who's done research in this? Art? Historical? Cog psych? It seems like there's something revealingly human in this.
Anyway, I would like to see the analysis re-run with triples. The author even says:
> for just three colors, there are more possible palettes than there are atoms in the universe