It’s hard to overstate how much color is lost over a few decades on film from that era. Even Technicolor, which was relatively low-fade, still fades (and was a little screwed up to begin with, as Technicolor was well past its prime at that point). The colors you see in these preservations are reconstructed. Yes, with lots of effort, care, and knowledge about how the films ought to look, but still reconstructed to some degree.

There was color variation on opening day. Technicolor prints (which, as I mentioned earlier were a little screwed up at that time) had a yellowish cast to them that you wouldn’t have seen on an LPP print, and so on.

So basically the color grade of a preservation is in the eyes of the grader. 4K77 has has a lot more people, and a lot more iterations on its color grade, so IMO it looks better. SSE has sort of receded into the background as far as fan attention goes, and its color grade hasn’t been revisited, so IMO it looks worse. Which of them looks more like an opening-day print? Almost certainly one of the more recent 4K77 iterations, but I’d say there’s still quite a lot of room for improvement there, too.

It’s an inexact science, starting out from a point very, very far from where the color really ought to be. It’s a miracle we even get something close.