It's really difficult to say which is the right color reference for a given movie... you can't trust your memory, so you must find some kind of reference. Photographs taken at the theater could in theory be a proper one, but could an analog camera take a reference picture in a dark theater, without flash?
Then there are production stills, documentaries, books, magazines... back to "simple" reference, I tend to think the oldest, the better - in term of color reference... see, for every new video format there is a new version that claim itself "the best, the most close to the theater experience", and often the director and/or the director of photography says "I approve it, this is the definitive version"... the problem is, it could happen two, three, even four times, and everytime each version is different from the former, even if each is THE definitive version... so, which is THE right one?
I think that, with year, directors - as they are human beings like us, did you know? - began to grow old, and tired, and when they were young they were all involved in their movies, from the beginning to the end of production and after... then, when they grow old, if a young representative of a studio go to them and say "Mr. Director, we'll release a new version of your movie... this time it's THE definivie edition, with the best video quality, the right colors, the greatest sound... just sign here, and here you are your check!" what could they do? Just sign the paper, and take the check to their bank... (^^,)