When Cynthia Erivo signed on to play Elphaba in Universal’s big-screen adaptation of “Wicked,” she knew one thing: she wanted to be green.

But Erivo actually wanted that are green, and don’t let the color be applied to her skin in post. So the film’s makeup designer, Frances Hannon – who was excited by the actor’s insistence – took on the challenge of finding the right shade of green.

Hannon made a checklist: the makeup couldn’t look like it had been painted on; the shade of green should compliment the “extremely beautiful” qualities of Erivo; and the color needed to work in any light. The product also had to last all day and not transfer to Erivo’s co-star Ariana Grande, who plays Glinda, or the elaborate costumes designed by Paul Tazewell.

There was just one problem, Hannon says: “The product didn’t exist.”

Hannon was already in pre-production on the film – a prequel to ‘The Wizard of Oz’, which tells the story of Elphaba and Glinda before they became known as the Wicked Witch of the West and Glinda the Good – when Erivo signed on . Since the Broadway character is, quite famously, dyed green, Hannon was already busy mixing shades and working with models to see how the products would work for film.

“I thought the green matched the skin tone, but I couldn’t make it work in all the different lighting,” says Hannon. “It would look beautiful inside, but outside the shadow looked gray, and in the sunlight it might look blue.”

After endless searching, Hannon found a discontinued Canadian product. “It was a cream eyeshadow,” she says, explaining that the essential ingredient turned out to be neon.

When Hannon discovered the green she wanted, she turned to famed British makeup manufacturer and developer David Stoneman for help in recreating it.

“He took the base from the small eyeshadow, which was neon yellow – just a few drops of it – and added it to the green shade. That was the perfect shade. It worked in any light,” says Hannon. “You could also apply it very thinly and it would stay green.”

Stoneman also created a green primer that smoothed makeup on the skin. “We airbrushed the very fine green on it. We contoured, powdered and sealed as needed,” says Hannon.

Erivo’s transformation took up to two and a half hours each day in the makeup trailer, but it wasn’t just about turning her skin green — Hannon and Erivo wanted to give the character a visual arc as the film progressed. The green base color never changes, but Hannon added subtle details like freckles and eyebrow transfers. “The power of her lips, eyes and nails became darker,” says Hannon, noting that as Elphaba discovers her power, her nails become stronger and longer.

The wigs were also key to designing Elphaba’s look, and getting them right required a huge amount of research.

“Cynthia is small,” Hannon says of the 6-foot-2 actor. “She had a big hat and big dark clothes and we didn’t want to lose the character.” Micro braids were the solution, she says: “It kept (her hair) close to the head and out of her face. It kept the hat and costume from drowning her, and left room for Elphaba to develop.”