The colors are very similar to those of the 1977 bootleg, albeit slightly less yellow. However, both the bootleg and the above photos point to a warmer yellowish tone:
Do you think that might be something to do with the actual technology of the time though? Pretty much every film from the 70’s has a yellow tone. That is too much of a coincidence.
I know when I went through Hell with Enter the Dragon with Color and Contrast issues and that is from 1973 and it’s obviously a different film all together but Blues were always quite muted from this era of film and Reds are way up with Greens. It’s like the Blue Color Spectrum did not quite make it to 70’s films.
At which point does Brightness and Contrast get introduced to a film scan?
I have no idea but I can imagine Brightness and Contrast easily being a factor introduced with either different scanning technology and / or better scanning technology. Nobody wants the horrible Contrast of the Old VHS days. The fail safe being Put the contrast and brightness up really high probably to avoid losing information when transferred to tape or simply the transfer technology was awful by today’s standards.
I think whatever analysis you are doing you are very much ignoring Brightness and contrast and are getting a bit confused by Color Bleed from Bad contrast issues. It’s messing your calculations up and you are not taking in to account how bad contrast can screw it all up. If it’s not neutral contrast you will have color Bleed and color that should not be in the image.
Rule of thumb 70’s films yeah Blue is missing in action.