skoal said:
How often do we have an accurate reference on how it looked in theaters?
Almost never. Discussions on this forum mostly revolve around cases where it is blatantly obvious that something is wrong. The 2nd dvd/1st bluray of Ghostbusters amps up contrast to detail crushing extremes, and many complained. This was fixed with the later 4k bluray. Other threads talk about improperly modern (teal/orange style) recoloring of old films. As you mention, it is often impossible to know what the original colors of a film are, but sometimes modern tinkering looks very wrong on old films and colors of earlier releases are preferable.
If you want to continue this topic, it would probably be a good idea to make a new thread in off topic, as this sub-fourm is more for active preservation or projects.