Costume designer Arianne Phillips is no stranger to working on midcentury films. From Brad Pitt’s Hawaiian shirt in “Once Upon a Time in Hollywood” to Reese Witherspoon’s perky frocks in “Walk the Line,” she’s at home with a variety of 1950s looks.

For Olivia Wilde’s dystopian thriller “Don’t Worry Darling,” opening Sept. 23 after bowing at the Venice Film Festival, Phillips channeled a look that was grounded in that era without being ultra-realistic. The film’s stars — Wilde, Florence Pugh, Harry Styles and Chris Pine — look like they’re living a carefree Rat Pack lifestyle, but something is off-kilter.

In a seemingly idyllic desert town, the men go to work each day at a company known as the Victory Project. The women clean their immaculate houses, take ballet lessons or sip martinis by the pool. When one woman disappears, Pugh’s character, Alice, starts asking questions.

In this land of endless springtime, the women sport colorful, flowered ’60s-style shifts, belted shirtwaists and pastel capris. The men wear casual bowling shirts or “Mad Men”-style suits.

Phillips invites audiences to pay close attention to the costumes for plot clues. “They can often be a device to distract from what’s really going on,” she says. “I used a lot of color control to guide tone and create the story arc.”

Multiple color palettes are used to tell Alice’s story, Phillips explains. “At first, I worked in a primary palette that was very bright and exciting. It was very reflective of Victory and that Palm Springs world that you think of when you see Victory.”

Makeup department head Heba Thorisdottir applied warmer tones to Pugh to complement the wardrobe. “She has pink- and peach-colored lipsticks that contrast with the others’ red lips,” Thorisdottir says.

Alice’s journey with makeup parallels the mystery of Victory unraveling. Says Thorisdottir, “She starts out with pinks, peach and shimmery white and black liner and slowly starts to unravel into a no-makeup look with muted and natural tones of browns and beige.”

Florence Pugh’s costumes by Arianne Phillips and Heba Thorisdottir’s makeup tease the film’s secrets. Merrick Morton

Phillips created the ’50s-style yellow floral apron Alice wears as she cooks — something that’s deemed pretty enough in this world to greet her husband in. “There was a lot of pressure to get the perfect apron,” Phillips says. “There’s always one thing that holds so much story, and the seemingly simplest thing can be the hardest.”

Together, Jack and Alice, Phillips says “are a perfect couple.” Styles’ Jack is charming and likable, outfitted in pastels including a sky blue suit. Phillips tapped Western Costume’s Jack Kasbarian to cut and make all of Jack’s suits. Kasbarian had worked with her on “Once Upon a Time in Hollywood,” tailoring Leonardo Di Caprio’s suits.

Arianne Phillips called on Western Costume’s Jack Kasbarian to cut and make all of Jack’s suits. Merrick Morton

Phillips delved into formal- wear for the Victory party night, a time when the town comes together to celebrate Jack and his future with the project. The glam affair gave her a chance to show a different side of the characters. “You see how they’re dressed,” she says, “and it tells you a little bit about them — when we dress up and show our best selves.”