Define, check and (automated) correct string-values for the tag "colour" (for buildings, ...)

Not necessarily - if the changeset description made it completely clear what it was changing and why, and not just “fixed tags” or similar (and perhaps even linked here!), then people should be able to figure out what is going on.

No, not for 53 objects :smile:

Practically, if you look at the distribution via taginfo / overpass you may be able to do it in 2 or 3 much smaller ones.