YouTuber thomas is insane made this side-by-side comparison of the theatrical and Snyder cut of Justice League of the scene where Superman fights the Justice League. Not only is the color grading totally different, but Joss Whedon added in a bunch of "comedic" inserts with his reshoots. The biggest difference is probably that Superman doesn't say a single word in the Snyder cut whereas Whedon decided to treat us to a bunch of reshoots so we could see their attempts at digitally removing Henry Cavill's facial hair which, honestly, might be the funniest parts of the whole movie.
Anyways, if you haven't watched the four hour Snyder cut what are you even doing? Having a life? Doing things? No thanks. I'd rather spend four hours watching Zack Snyder indulge himself followed by another four hours of him doing it again in black and white. That's right, if you weren't aware there's also a black and white version of the Snyder cut that's the exact same movie but in black and white and called Zack Snyder's Justice League: Justice Is Gray. Really rolls off the tongue.
Keep going for the full side-by-side comparison.