The current Princess of Wales has been known to channel her late mother-in-law through her wardrobe, but still mostly adheres to a style guideline that Diana often sidestepped

Kate Middleton and Princess Diana. Photo: Max Mumby/Indigo/Getty; Martin Keene – PA Images/PA Images via Getty

Kate Middleton often channels her late mother-in-law, Princess Diana, when it comes to fashion — but there’s one style rule Diana broke frequently that Kate still for the most part strictly follows.

Fashion designer Dame Zandra Rhodes said, per Hello!, that Diana loved little black dresses, but that the former Princess of Wales wasn’t supposed to wear black unless she was in mourning or at a funeral.

“She was very shy,” Rhodes said of Diana. “She would come into my shop in Mayfair and go through the rails. Sometimes she picked something in black, which the royals weren’t allowed to wear except at funerals, so we would make it in her size in a different color.”

While Diana was ever one to go her own way, when it comes to dressing as a member of the royal family, her daughter-in-law Kate “appears to keep to the rules more than her husband’s mother,” the Daily Mirror writes, adding that, when it comes to the color black, the current Princess of Wales mostly only wears the hue “when it mourning and at funerals.” Hello! adds that Princess Kate “has a wardrobe full of rainbow-hued clothing and chic neutrals” and, when it comes to not wearing black except at funerals, she almost “always adheres to the unspoken rule.”

Kate Middleton during a visit to Army Training Centre Pirbright on September 16, 2022.Samir Hussein/WireImage

Kate wore black to the funerals of Prince Philip in April 2021 and Queen Elizabeth in September 2022, and wore the color throughout the mourning period for the latter as it lasted throughout the month. The Princess of Wales also wears the color for annual Remembrance Day events, and though she has worn black outside of somber occasions, it’s rare. Instead, Princess Kate often leans toward the late Queen Elizabeth’s fashion rule of wearing bright colors to stand out in a crowd.

Though Kate hasn’t largely adopted her mother-in-law’s penchant for wearing black, “I think we have seen lots of examples where the reference is very intentional, and I think that Kate uses fashion to pay tribute to Diana in a very positive way,” Bethan Holt, Fashion Director at the Daily Telegraph and the author of The Duchess of Cambridge: A Decade of Modern Royal Style, previously told PEOPLE.

Holt added that “What’s really key about these times when Kate references Diana, it’s not like a costume. She brings it right up to date so she makes it look relevant for now. She’s not doing an ‘80s power shoulder or a puff ball skirt, she’s making it look sleeker and more contemporary. She makes it her own without looking like she’s playing ‘dress up as Diana.’”

Kate Middleton and Princess Diana. Chris Jackson/Getty; Tim Graham Photo Library via Getty

Though Rhodes said royals “weren’t allowed” to wear black unless in mourning, Diana disregarded that rule as early as 1981, back when she was still Lady Diana Spencer and not long after she became engaged to then Prince Charles. Diana wore a black gown by David and Elizabeth Emanuel (who went on to design her wedding gown in July of that same year) to a fundraising concert on March 9, 1981, which marked Charles and Diana’s first public engagement together.

Prince Charles and his fiancee Lady Diana Spencer attend their first public engagement together on March 9, 1981.Getty Images

Upon seeing the off-the-shoulder taffeta look she wore that evening, the former Prince of Wales told his future wife, “Only people in mourning wear black!” She wore the dress anyway and would wear the color many more times throughout her royal life, eschewing protocol — perhaps most memorably in 1994 when she wore what became known as her “revenge dress” at London’s Serpentine Gallery in June of that year.

As PEOPLE reported, the fitted, black, off-the-shoulder Christina Stambolian dress with an asymmetrical hemline and chiffon train was unusual for a member of the typically buttoned-up royal family to wear, and the revealing look was worn on a very poignant evening: the same night Charles confessed on national television that he had been unfaithful to her in their marriage. “It is a deeply regrettable thing to happen, but it does happen, and, unfortunately, in this case, it has happened,” the future king said.

Princess Diana in the “Revenge dress” in 1994. Princess Diana Archives/Getty Images
“On a human level, for Diana, you can only imagine how upsetting that would have been, not only to hear that, but to know that now the world has heard it,” PEOPLE’s Executive Editorial Director Michelle Tauber previously said. “Effectively, Charles has aired some serious dirty laundry. Some may have decided this was altogether too much and tried to avoid the cameras, stay out of the limelight — just let the storm pass. That is not what Diana chose to do that night.”

Kate Middleton waves to fans at Wimbledon on July 14, 2024.Shi Tang/Getty

Like with Diana, ample thought goes into Kate’s wardrobe, and at her most recent public appearance at Wimbledon last month, she opted for a purple Safiyaa dress, which Holt previously told PEOPLE was “the color of courage”: “I think she looked glowing and radiant, and it was lovely to see her looking so relaxed,” she said. “I’m sure lots of people will have seen how happy she looked and taken reassurance from that. She really is a kind of beacon of hope for many, but that also comes with a lot of pressure.”