In the new indie film “Promising Young Woman,” set for a Christmas Day release, production designer Michael Perry plays with color to show the lightness and darkness of the main character’s life.

That meant using bold hues to portray an emboldened Cassie, the film’s protagonist, played by Carey Mulligan, who drops out of med school and spends nights seeking revenge on would-be rapists following an attack on her friend. Perry introduced warm colors in not-so-safe spaces to make them less menacing to viewers.

Working with director Emerald Fennell turned out to be a dream for Perry, because she was open to a wide range of ideas for her feature directing debut.

For Cassie’s house, Perry found a place in Los Angeles that he describes as being “trapped in time.” In one scene, Cassie brings her date over for dinner, and the table has a plastic cover that looks like “a 1950s version of American life.” Paintings of dogs on the wall added to the film’s off-kilter narrative. The layout of the house was also key to reflecting Cassie’s state of mind. “It [enabled] great long shots where you could go from the kitchen and all the way back into the living room,” Perry explains. “You felt that she was in limbo there and not participating in life.”

Perry showed Fennell stills from “Murder She Wrote” with pink and blue hues that informed his color palette, especially in Cassie’s bedroom, which revealed much of who she is: a woman on a mission — an avenging angel. On the surface, the room looks like a safe place, with childhood pinks, but a backstory to her vengeance comes to light, and Perry reflected that in his design motif. “All her pain and vulnerability is there,” he says. “There’s a lot of angel wings and Joan of Arc.”

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Carey Mulligan, Emerald Fennell and Laverne Cox share a laugh on the film’s coffee shop set. Courtesy of Merie Weismiller Wallace / Focus Features

The designer planned to have a scene that’s set at a cabin in the woods look warm and nature-like, so he decorated it in plaid with earth tones. “I didn’t want to give away where we are going with the movie — it’s like the honeymoon cottage,” he says. But the cabin is far from a romantic spot, so the cozy atmosphere gets turned on its head.

A set Perry says was “very much thought out” was the coffee shop where Cassie works, offering subtle clues, again including color schemes, to help the viewer understand who she is. He had a full day to dress it, and much of his prep went into working on sketches and having things manufactured and ready to go on the day of the shoot.

“I loved the idea of her being among the odd blue with touches of red on the coffee cup and in the restaurant, just so you know there’s a danger coming,” he says. “But she could hang out there; it was safe and she could be hidden.”