The meaning behind their matching green

Kate Middleton and Queen Camilla caused a style surprise by coming together for the royal family’s traditional Christmas Day outing.

On Dec. 25, the 42-year-old Princess of Wales and the 77-year-old queen wore deep green coats with matching hats for a morning service at St. Mary Magdalene Church on the Sandringham estate, where British royals have celebrated Christmas for generations. It was a rare matching moment for Princess Kate and Queen Camilla, who each completed their look with black gloves, boots and handbags.

Princess Kate arrived in a forest green button-down coat by Sarah Burton for Alexander McQueen (her wedding dress designer), while Queen Camilla wore a festive moss green wrap coat to lead the way to church with King Charles.

Spot-on color coordination between the Princess of Wales and the Queen is rare, as they usually opt for different hues at public events.

Although Princess Kate has only appeared in public a few times this year after undergoing cancer treatment and completing chemotherapy, her meeting with Queen Camilla at Christmas was no coincidence. The royal family carefully coordinates their outfits before important public appearances and the moment the women came together was a sign of family unity.

Kate also coordinated with her husband, Prince William, and their children, Prince George, 11, Princess Charlotte, 9, and Prince Louis, 6, alternating shades of green and blue.

As the Princess of Wales continues to recover, she is also preparing for her future role as queen. After Queen Elizabeth’s death in September 2022, Prince William and Princess Kate moved closer to their future duties as king and queen. When William’s father, King Charles, announced his own cancer diagnosis in February (while treatment for an unknown form of cancer was still ongoing), that path came into clearer focus. Queen Camilla, 77, also recently had to miss several royal events due to pneumonia, which once again highlights the family’s vulnerability.

“Although the King carries out his duties with typical determination, he has faced limitations during his cancer treatment. As a result, William has taken on more responsibility and he and Kate have prepared for their future roles sooner than they could have expected,” royal biographer Sally Bedell Smith tells PEOPLE about the Prince and Princess of Wales’s year like no other.

“There is a feeling of calm before the storm. They face the biggest task of their lives next, and of course Kate’s health is a priority, but it will also allow everyone to take a step back and figure out what’s important right now,” says an insider.

The transition to the throne will inevitably come, although it remains complex and carefully considered.

“The institution is always aware of this,” a source close to the matter says of the frequent updates of plans. “It’s an institutional readiness.”

“Your circumstances will change at some point. Looking ahead, it would make a lot of sense to rebuild slowly and prioritize family time,” the source adds.

Friends and sources say Princess Kate’s experiences have changed both at home and in her approach to royal duties and that for her, family comes first.

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“Life-threatening illnesses cause priorities to be reconsidered. She and William have always made it clear that family is the most important thing,” says a source close to the royal household.

Looking ahead, she will take on more public roles when she is ready and her doctors give the green light.

A second source close to the household said: “She needs to get the situation back under control. And she will if she is left alone to handle it herself.”

Dive into royal holiday traditions with the special edition of PEOPLE: Christmas at the Palace: A Royal Family Album.