I would be a little cautious regarding the stills in the Making of book--they look like they are from a low-res video source. My guess is that they are simply taken from a Laserdisk, and that is certainly what it appears to be, which is why the screenshots are always small on the page, the few big ones have clear video noise, muddy detail and soft edges that give it away as an old analog video transfer. The binary sunset scene screen they have looks very similar to the cap above strangely, but maybe they just used the oldest video source they could get because they knew colors had been tweaked for the GOUT.
Also, older editions were slightly brighter because of home video practices of the time. Any transfer of any film from the 80s was artificially brightened a little so that it was more visible when viewing it during the day, whereas by the 1990s this was less pronounced (which is why the garbage mattes are so apparent on early home video and broadcast transfers, but less obvious on later releases).
My opinion is that the film has become dimmer with each transfer through the 1990s, at least in select scenes, but it's a bit difficult to know exactly by how much. The 1993 GOUT seems pretty faithful from all the stills, 70mm frames, and other photo material not from home video, even if some of those sources are faded.
Also, the binary sunset shot, aside from the second sun, is not trick photography. It's a real sunset, taken at the end of the day, so there's not severe exposure manipulation going on, aside from perhaps a bit of compensation to get the sky to photograph. It looks like they were using either an amber or a violet gradient filter, IMO, because some of the grad in the top left corner looks weird, it goes dark like it is something in front of the lens, almost like a vignette, and not the natural sky grad.
That photo doesn't exhibit that though. In fact, it looks almost black and white, and it's too sharp to be from a video transfer from 1993. In fact, it almost looks like it is one of the black and white set photos that has been tinted to approximate the look of the scene. This makes sense when one considers that they were photographing a real sunset in the desert--there should be pretty pronounced color. Especially if they were enhancing it with a filter, which is sort of what it looks like. That the photo does not have the grad artifact on the top left, IMO makes me suspicious that it is not from the actual film negative.
The only solution is this: the photo is actually from the negative, from a camera negative, while the final print was graded in post with a filter to give it more color. This would explain why the 2004 version doesn't have the grad--it wasn't in-camera, as they went back to the negative. This would also explain how the book photo is so sharp, how it adheres to the framing of the film but actually reveals more vertical area (that would normally be masked in projection or video transfer), and why it has less color. It would still be very strange that there was so little color from an actual sunset. And of course all these reasons could also explain why it is a set photography.
Okay, I'll admit it. I'm a bit sumped stumped. But IMO, it's not accurate to the final answer print of the film. The GOUT looks like it has had the saturation bumped up, but I don't think I've ever come across material that makes the scene look almost black and white. There was always a hint of some strong color there, even if it was way less pronounced. That's my impression, anyway.