I just stumbled across this thread, and it’s never dawned on me that the film master represented a unique version of the film. My only gripe previously was with the few changes made by the re-rendered version of the film in 2010. To which I will re-iterate: the worst part is the new Disney logo that clips out part of the original film. Then there’s little animation errors. One that I found on my own is that they swapped out the textures for Janie so her dress will randomly change colors in one scene (another example of color grading as well):

And it’s also a different experience when the models are in such crisp high resolution as they’ve never been before, but the textures are now noticeably low res. That one’s a little more of a nitpick, though.

Originally, I just wanted to see the original theatrical render of the film on Blu-Ray. The original resolution was just a touch more than DVD could handle, and we never got a Blu-Ray release of that original version before it was replaced by the re-render. If I’m correct, the Toy Story 10th Anniversary DVD from 2005 is the best presentation of the original render. Which is why I think it’d probably make the best basis of a complete color grading overhaul since it wouldn’t have those aforementioned issues with the re-render and it would be closer in resolution.

On a related note, the new-ish UHD release of Toy Story in 4K has a notably different grading. To my eyes, it looks closer to the film version, but that might just be me.
https://highdefdiscnews.com/2019/06/06/toy-story-4k-uhd-blu-ray-review/