Earlier quoted context omitted.
I think you're ill-informed. The Pixar movies were re-rendered completely. They did not take a 35mm negative, or an old file, to transfer it. Pixar has the ability to load the Toy Story project files, and use the current version of RenderMan to make a new final version. It's completely unique among the industry.
But IIRC there was some color grading gaffe because the original colors were precompensated for film ( they originally filmed the renders ) - but this lead to oversaturation and color changes in the digital renders. So in some way they did meet a similar fate.
They would have needed to look at the 35mm negative of Toy Story from '95, picked up the colours from there to then put an intermediate colour correction step. They didn't do it, which is a shame. We lost artistic intent.