In Wicked, wicked-witch-to-be Elphaba (Cynthia Erivo) is ostracized by her fellow Ozians because of her green skin and her magical powers. But on the set of a big-budget Hollywood studio production that leans heavily on visual effects instead of magic, she has her own viridescent foe: green-screen technology.Vivid green backdropsoften referred to as chroma green by digital artists are used in modern VFX processes, in part, because that tint is so far from the color range of human skin. That makes it far easier for visual effects artists to digitally select anything in an image thats chroma green and replace it, keying out the actors and placing them into new backgrounds. But if Elphaba stood in front of a green-screen background, it would likely erase her like her classmates want to, theoretically leaving a just-as-magical floating hat, eyes, dress, and cape standing in for the Wicked Witch of the West.As Industrial Light & Magic visual effects supervisor Pablo Helman told Polygon in an interview ahead of Wickeds release, Elphabas coloration made it necessary to revert to an earlier form of this kind of digital replacement technology.It immediately became a blue-screen show, Helman says. When youre doing prep, you have to acquire all these screens. And so we knew that we had [to use] blue screen.Helman, whose credits in visual effects range from fantastical movies like Star Wars: Episode II Attack of the Clones to less visible work on Martin Scorseses The Irishman prefers to use these screens as little as possible: The reason why I dont like [this method] is because it changes the lighting by spilling all over the set, one color or the other. In his eyes, that would have sucked the life out of one of Wickeds most elaborate musical numbers, where prince Fiyero (Jonathan Bailey) leads Galinda/Glinda (Ariana Grande) and others in a cheery song about how Lifes more painless / for the brainless.For instance, in scenes like Dancing Through Life in the library, it could have been a blue-screen set, because all the backgrounds were put in there, Helman says. But I worked with Alice Brooks, the director of photography, just to say, If were thinking that were exposing for the inside, and the outside is going to be blooming, lets just light it white, and lets deal with extracting the actors and putting backgrounds differently, because then the white light is going to help us in having the true meaning of what it means to be in a set like that.The contrast between the bright white light Brooks and Helman wanted for that scene and the blue light that digital-friendly backdrops would have spread across the sequence is part of the frustration Helman often sees on movie sets, where different needs for a shot can come into conflict. If you actually go historically to the beginning of green- or blue-screen photography, its because in visual effects, we like to separate everything, and we love to have control over everything, he says. But the director also wants to have control, and the production designer wants to have control.Even with all the preparation Helman, director Jon M. Chu (Crazy Rich Asians, In the Heights), and the rest of the filmmaking team put into the project, it wasnt until they were on set that they discovered how avoiding an Elphaba green-screen clash meant running into another problem.Until we started shooting in Shiz [the university in Oz], we [hadnt] realized that everybody was wearing blue, Helman laughed.