Tonino Delli Colli's Techniscope cinematography for The Good, the Bad and the Ugly has been restored from the original camera negative (or "OCN") by L'Immagine Ritrovata, the imaging specialty facility created by the Cineteca di Bologna for precisely such projects. Delli Colli died in 2005, but the restoration team consulted with Sergio Salvati, assistant cameraman on the film. They also used Italian Technicolor prints as a color reference. (Far too many internet discussions of classic films complain about the colors on Blu-ray without any basis other than personal preference.)
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Third, the color balance has changed dramatically, a point that has already engendered much comment, primarily from viewers who have seen screen captures but not the disc itself. Yellow has been prominently accentuated throughout, although not (as some have claimed) to the exclusion of all other colors. Screenshot 3 accompanying this review shows an example of a frame bisected by a contrast between a yellowish-brown foreground and the bluish cast of the distant hills, as Lee Van Cleef's "Angel Eyes" dismounts his horse in his first appearance. Deep blues recur repeatedly, both in night scenes and whenever the Union Army appears.
The yellow cast has been confirmed as Leone's intent, which was not reflected in the prior Blu-ray, just as the framing was wrong. If one stares at screen captures, then it seems to jump out, but if one sits down to watch the film straight through, the eye quickly adjusts, as other colors vary and balance the image. By the end of a three-hour viewing, you are no longer aware that anything has changed (until, that is, you put on an older copy).