[kazinator]

OK, so it tracks key changes? How about secondary dominants: V-I cadences targeting any scale degree at any time.

[recursive]

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.

[vitaly-pavlenko]

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.

[kazinator]

OK, so this is a case of personal knowledge transfer, which is valuable for that reason. You take your expert opinion that certain things are happening functionally in the music, and encode it in color.