In the 80s transfers, the telecine operator cranked up the gamma during dark scenes. I don't think there's any way to make that shot look accurate - I'm finding that some scenes in these transfers can have fairly accurate-feeling colors coaxed out of them, but others can't. The film colors didn't accurately carry over in the transfer, and it does seem like some color adjustments were made in the video realm - not as severe as 90s transfers, though.
The THX DVD documentary clips look about the same as the ones in Empire of Dreams. Both of them used a different source than the official video masters - for example, Jabba's subtitles were burned in like they were in theaters.
It's the weirdest thing - for the binary sunset closeup, if I go into Microsoft Office Picture Manager, use the Enhance Color tool, and click on the cyan sun as the area I want to be balanced to white, the whole image changes to a more accurate palette.
Again, ignore stuff like color blocking, the pink halo around the sun, etc., this image is auto-corrected by the program using the sun as a point of reference for white balance.
However, it only works with that one shot - using Picture Manager, which is the only image editing program I have (and it's not really a very good one anyway), I can only add or subtract one hue at a time, and I can't get a manual result that matches this automatic correction
By this process of manually adding or subtracting a certain hue, then another one, and so on, and constantly tweaking the brightness/contrast/etc., this is the best I could get out of the middle image from the THX disc (I cropped out the "Star Wars (1977)" caption):
Brightness, contrast, saturation may not be accurate, and once again there's posterization and other artifacting, but I'm working from a considerably darkened image with less contrast detail in it. This is the closest I could get as far as color temperature - matches what I've seen, but not as much color range (for example, the coolness of this version's timing means that I couldn't recover the blue-to-purple gradient in the sky, if I wanted more of one, I had to give up more of the other.)
The wide shot was digitally recomposited and retimed for the SE, and the colors were totally altered. Thus, I can't tweak it to approximate the original colors. Besides, there's no point in doing so, since Harmy already corrected the scene for DeEd 2.0, and that's the closest the SE version of the scene will ever get to looking like the '77 colors.
Even if I had better image editing tools and knew how to use them, I don't think that a certain color curve would magically change the THX/EoD clips to an accurate palette. Even if Technicolor prints were used as reference, the film was still retimed and Mike Verta says it's not accurate to the original colors. Still, I wonder how many scenes still retain some of the accurate colors "hidden" in the image.