It's rainbow if we skip coloring 1 and 5 and color them with grayscale instead.

Here's the question. If we can allow one color not to be "colorful" (chromatic), what pitch would that be? It's the tonic (pitch 1).

If we allow two such colors? 5 is a good candidate, it's present in almost all popular scales. (Locrian isn't very popular.)

The rest 10 colors go in rainbow by thirds, as you proposed.

So, using two grayscale colors, I've reduced the demand to make distinct enough color palette from 12 colors to 10 chromatic + 2 grayscale.

Which (10), in my experience fighting with different screens and projectors, is almost the limit of having something stable, distinguishable, nameable and memorable.

Funny enough, those 10 can be further split into 5 brighter and 5 darker pitches. Exactly as they turn from bright to dark if we go from bright to dark modes: https://www.dropbox.com/scl/fi/dku7jezn00yltb607j2un/Screens...

So here I stand with dilettantes :)

Being a jazz college dropout, I stopped building around standard notation when after two years of training - and I started learning piano at 25 - I still didn't get any fluency in instantly seeing harmonic structure in the scores.

I don't care that much about articulation. I can hear articulation anyways. What I care about is the elusive layer of harmony which is so hard to reason about without the right tools.

That's why people do Roman numerals, figured bass, all sorts of annotation: https://github.com/vpavlenko/study-music/blob/main/parts/cla...

And that's what I was chasing. Something that gives me, a guy who didn't spent formative years of K-12 by sight-reading at the piano, a way to build mental models of how Western harmony works.

And here, I believe, I'm with the majority of people.

In all cases of tonicization I decided whether to notate a brief tonic change or not (piece by piece, case by case): https://rawl.rocks/s/applied/chain_of_dominants

You can always manually "probe", minutely "recolor": click on a measure number and hover a potential new tonic.

I might be using the terminology wrong, but I wouldn't call a I-IV resolution V-I, even though it's the same relative movement. Nor would I call it a key change. I would say downward movement of a fifth is common in western music, but the feel is different for different resolution targets. To me, it seems more clear or explanatory to keep the colors encoded as scale degrees of the current key, not the local cadence-resolution-target or whatnot.