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The forthcoming "Mean Girls" musical inspired by the 2004 Linday Lohan-helmed film (left), stars pink-clad pals, Kate Rockwell as Karen, from left, Taylor Louderman as Regina, Erika Henningsen as Cady and Ashley Park as Gretchen.

Forget shades of gray: Think pink!

That’s what Gregg Barnes did. For the Tina Fey musical “Mean Girls,” the Tony-winning costume designer concocted a rainbow of shades for Queen Bee Regina George and her high-school posse, the Plastics.

And while Barnes somehow missed Fey’s hit flick when it came out 14 years ago (“I bought it on Amazon after the first table read, maybe two years ago”), pink was something he knew plenty about: After all, he designed the bubble gum-colored costumes for Broadway’s “Legally Blonde.”

After a heady tryout last fall in Washington, DC, “Mean Girls” — the musical — is in previews at the August Wilson Theatre, where it opens April 8. While the story’s the same as it was in the 2004 film, the stage adaptation’s been updated to reflect the present.

So have the fashions.

Gone are the film’s pointy pumps, tight sweaters and chain necklaces that Barnes calls “very ‘Devil Wears Prada.’” He decided that those looks were too mature-looking for today’s high schoolers — and gave them instead to Kerry Butler to wear as Ms. Norbury, the put-upon schoolteacher Fey plays in the movie.

Most of how he dressed the cast came from the actors themselves and from what they wear in real life. “Taylor Louderman, who plays Regina, wore a pair of very stretchy, tight denim jeans at one workshop,” Barnes recalls. “Tina said, ‘Her legs are great. We should remember that.’”

The actors were also asked to write about themselves and the kinds of clothing they liked to wear. “We sort of came up with places we thought that the individual kids would actually shop [at],” Barnes says. “So, we have, ‘This is the catalog girl,’ ‘This is the Free People girl,’ ‘This is the Lands’ End boy.’ ”

Some of the clothes bought off the rack were tweaked or completely remade, including one of Regina’s sweaters. The original came from H&M and cost $29, Barnes says, but it couldn’t hold up to eight shows a week. “So, our knitters turned it into a many-more-dollars sweater,” he says, “beefing up the color and improving the fit.”

The look for leading lady Cady, portrayed by Lindsay Lohan in the film, was something else entirely. We first see Erika Henningsen’s character in Africa, clad in what Barnes calls “a hideous vest, cargo shorts and sandals with socks.” Once she gets to North Shore High School, she wears a series of flannel shirts, each one more fitted than the next — a metaphor, Barnes says, for how Cady is shaping herself into one of Regina’s cronies.

Barnes and his crew hewed closely to the styles worn by the film’s goth character, Janis, played by Barrett Wilbert Weed. After shopping “all over the planet,” they settled on a Ralph Lauren denim jacket they took to Jeff Fender, Broadway’s go-to fabric painter who has also created stage looks for Madonna and Lady Gaga. Not only did Fender distress it, he painted all over it, just as Janis, the art student, might have — with an angel on one sleeve and a devil on the other.

Janis’ gay best friend, Damian — whom Barnes says is modeled on Fey’s own high-school pal — wears T-shirts emblazoned with his heroes, Judy Garland and drag queen Bianca Del Rio among them. At one point, Fey requested they put actor Grey Henson in a T-shirt depicting what Barnes calls “a Grade-D horror film, ‘Summer Camp’ or something,” Fey’s friend’s favorite film.

And then there’s the school dreamboat, Aaron, played by Kyle Selig. “He’s probably the one character we didn’t have to restructure,” Barnes says. “He’s pure and simple, and probably his mom buys him stuff, so we shopped for him at Penguin and Abercrombie & Fitch.” And, since he’s a jock, and North Shore High’s colors are blue and yellow, you’ll see him wearing a lot of that.

One of Barnes’ favorite pieces is the Halloween cat costume worn by Kate Rockwell’s Gretchen, who calls herself “Regina’s aide de tramp.”

“The costume in the film is definitely out of a Ricky’s catalog,” Barnes says, referring to NYC’s delightfully outré chain of beauty and costume shops. But the show’s version is a custom-made outfit of stretch vinyl with a pieced leather corset.

End result: “I can’t get my eyes off her!”