The Princess of Wales’s wardrobe is one of the most dissected in the world, but Kate Middleton doesn’t tend to take her cues from the runways, or pay close attention to what the street-style set is wearing. Her unique position—Kate has to factor in diplomacy, practicality, propriety, and photography when dressing for a royal engagement—tends to mean sticking to what she knows, rather than ticking off trends. Don’t expect to see the Princess in a bonkers skirt or an ugly shoe, for example. (She went cold turkey on Sledge heels some time ago now.)

Hence we’re used to seeing the royal in slim-fit tailoring, fit and flare dresses, and Alexander McQueen coats, typically finished with suede Gianvito Rossi heels and a glossy blowout. But a royal outing for Kate and William this week (the same week they celebrated 15 years of marriage), revealed that one street-style favorite has the royal seal of approval too: the blue and brown color combination.

Just as polished as black but a more interesting choice, chocolate brown was everywhere last season, with Michael Kors, Victoria Beckham, and Saint Laurent all leaning into the decadence of the shade, and fashion fans duly curating all-brown looks for fall and winter. Now that summer is on the horizon, editors have been freshening up the look with a hit of light blue. Add the royal seal of approval—care of Kate Middleton—and you’re ready for garden season, too.

For a visit to the IntoUniversity charity with Prince William this week, Kate layered her spring-ready, pale blue Roland Mouret crepe blazer (a new purchase) over a simple chocolate-brown ME&EM sweater vest, and matching high-waisted pin-tuck Edeline Lee trousers. The effect was every bit as polished as black and white, but a little less predictable—and entirely appropriate for the sunny weather. She threw in another street-style essential: personalized jewelry. Her necklace was strung with three letter pendants—the first initial of each of her three children, George, Charlotte, and Louis.