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.

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.