Zosia Mamet tells Us Weekly why she went gray with her hair color. Credit: Brad Barket/Getty Images

Goodbye, blonde! Hello, gray?

Zosia Mamet is the latest celeb to jump on the gray-haired bandwagon a la Dascha Polanco and Tori Spelling (for a hot minute). The Girls actress, 26, debuted the new look on Sunday, Dec. 7, at the premiere of A Most Violent Year in New York City.

So what made Mamet, who had been rocking platinum blonde hair, want to switch up her look? "I got bored," the Armani-clad actress told Us Weekly. "I had very long 'brown virgin hair' my whole life, and after I got to be blonde for a play that I did, I loved it and wanted to do something different."

Although she initially toyed with the idea of going even blonder, she found inspiration in an unlikely place — mass transit. "I would often be on the subway and see girls with various hair colors and be super envious of that color. So I just decided that I wanted to do the colors that I always wanted," she told Us.

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Mamet wanted to try violet, but the shade was nixed by her hairdresser, who simply said, "That would look childish."

Instead, she opted for a mature style (granny-chic, anyone?) for Mamet on Wed., Dec. 3. "My colorist referred to it as 'antique gray,'" she told Us. "I'm still getting used to it; I think it's cool."