Princess Diana Was the Original Cobalt Blue It Girl

Princess Diana wearing three different blue dresses — (Image credit: Getty Images)

Whether you call it cobalt blue or Klein blue, 2026's biggest color trend is absolutely everywhere right now. But for members of the Royal Family, the electric shade has been a favorite for decades.

Princess Kate frequently wears the bright color, as did Queen Elizabeth, who notably remarked that she had to be "seen to be believed." But Princess Diana was perhaps the most fervent cobalt blue fan, wearing the color for everything from her 1981 engagement announcement to glittering evening galas.

Perhaps it was a touch of the late Queen's philosophy of being easily spotted in a crowd, but there also could have been a deeper meaning behind Diana's love of the shade. Relying on such a vibrant, impossible-to-miss color during her turbulent marriage to Prince Charles projected a brightness and confidence that wasn't there internally for the royal. Call it emotional armor, if you will.

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Explore some of Princess Diana's best cobalt moments, ahead.

Princess Diana and Prince Charles in their engagement photo — Princess Diana and Prince Charles are pictured in one of their 1981 engagement photos.

Diana had trouble finding what she wanted for her official engagement photo call in February 1981, and in a Pretty Woman moment, ended up being turned away from designer Bellville Sassoon's boutique and told to go to Harrods by an unknowing assistant. The future royal bride did end up buying an outfit at Harrods, choosing a bright blue skirt suit by Cojana and a white pussybow blouse for her big moment.

Princess Diana wearing a blue dress walking next to her sister Sarah McCorquodale — Princess Diana is pictured with her sister, Sarah McCorquodale, in 1992.

In 1992, Diana went for a bold blue look, wearing a double-breasted Catherine Walker blazer with a long, pleated skirt and matching blue pumps. Years later, Princess Kate would go on to copy the look, wearing a cobalt Zara blazer with a matching pleated skirt by Hope in 2021.

Princess Diana in a blue blazer and skirt — Prince Charles and Princess Diana are pictured in 1986.

During a visit to British Columbia, Canada in May 1986, Diana wore a very dotty look, pairing a cobalt skirt and a blazer featuring black spots with a polka-dot blouse underneath.

Princess Diana wearing a blue outfit and hat holding hands with a little boy in a crowd — Princess Diana is pictured in Wellington, New Zealand in 1983.

Diana leaned into the cobalt aesthetic two years after her wedding, wearing a bright blue dress with black trim and a matching hat on a tour of New Zealand.

Princess Diana wearing a blue dress on a boat — Princess Diana is pictured in Venice in 1985.

Princess Diana once again brought blue energy while visiting Venice, Italy in May 1985, wearing a dress with sharp shoulder pads designed by one of her go-tos, Bruce Oldfield.

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Kristin Contino is Marie Claire's Senior Royal and Celebrity editor. She's been covering royalty since 2018—including major moments such as the Platinum Jubilee, Queen Elizabeth II’s death and King Charles III's coronation—and places a particular focus on the British Royal Family's style and what it means.

Prior to working at Marie Claire, she wrote about celebrity and royal fashion at Page Six Style and covered royalty from around the world as chief reporter at Royal Central. Kristin has provided expert commentary for outlets including the BBC, Sky News, US Weekly, the Today Show and many others.

Kristin is also the published author of two novels, “The Legacy of Us” and “A House Full of Windsor.” She's passionate about travel, history, horses, and learning everything she can about her favorite city in the world, London.