Photo:Yui Mok-WPA Pool/Getty Images

Prince William, Prince of Wales, Catherine, Princess of Wales, Sophie, Duchess of Edinburgh and Prince Edward, Duke of Edinburgh watch as King Charles and Queen Camilla depart after the Order Of The Garter Service

Yui Mok-WPA Pool/Getty Images

Kate Middletonis the queen of the curtsy!

Kate curtsied again — alongside Sophie, the Duchess of Edinburgh while Prince William and Prince Edward nodded their heads in bows — on the steps outside St. George’s Chapel as King Charles, 74, and Queen Camilla, 75, took off in their carriage following the service.

Just as public citizens may opt to do whenmeeting a royal, it’s common to see members of the family showing respect while greeting each other — men traditionally bow their heads while women dip into a curtsy.

Kate Middleton, the Princess of Wales.Mark Cuthbert/UK Press via Getty Images

Catherine, Princess of Wales curtsies during the Order Of The Garter Service

Mark Cuthbert/UK Press via Getty Images

When royals don’t bow or curtsy to greet the King and Queen, there’s likely a logical reason why: they’ve probably already seen each other that day. In addition to the formal gesture, Charles and Camilla are often seen greeting family members with kisses on the cheeks or hugs.

King Charles and Queen Camilla.Chris Jackson - Pool/Getty Images

King Charles III and Queen Camilla arrive at the Order Of The Garter Service at Windsor Castle

Chris Jackson - Pool/Getty Images

On Monday, Princess Kate had a very different greeting when she saw Prince William, who will celebrate his 41st birthday this week, taking part in the procession — a big smile as they locked eyes!

The Order of the Garter has aspecial spot in the history of William and Kate’s relationship. In 2008, Kate attended the ceremony as Prince William’s girlfriend three years before they married, showing that she was being welcomed into the royal family fold.

Can’t get enough ofPEOPLE’s Royals coverage?Sign up for our free Royals newsletterto get the latest updates on Kate Middleton, Meghan Markle and more!

HENRY NICHOLLS/POOL/AFP via Getty Images

Catherine, Princess of Wales (C-L) and Britain’s Sophie, Duchess of Edinburgh (C-R) look at Britain’s Prince William, Prince of Wales (2nd R) and Britain’s Prince Edward, Duke of Edinburgh (R) arriving at St George’s Chapel to attend the Most Noble Order of the Garter Ceremony

Kate also reached for a special accessory: theCollingwood pearl and diamond earrings. The jewels previously belonged to her late mother-in-law Princess Diana, and Princess Kate has worn them on several occasions through the years — including at palace galas paired with a tiara!

Catherine, Princess of Wales during the Order Of The Garter Service at Windsor Castle

While William rode on horseback for the King’s birthday parade,Kate rode in the Ascot Landauwith Queen Camilla and her three children:Prince George,Princess CharlotteandPrince Louis.

Catherine, Princess of Wales and Prince William, Prince of Wales depart the Order Of The Garter Service at Windsor Castle

The bold color was no coincidence either — in fact, it carried quite a few meanings. Green nodded to her role as honorary Colonel of the Irish Guards as well as the nation of Wales, where green is a prominent color in the Welsh flags.

Some noted that the hue echoed the color that Queen Elizabeth wore to the same event last year, which kicked off her Platinum Jubilee celebrations.

Prince George of Wales, Prince Louis of Wales, Catherine, Princess of Wales, Princess Charlotte of Wales and Prince William, Prince of Wales watch an RAF flypast from the balcony of Buckingham Palace during Trooping the Colour

Kate completed the weekend look withsapphire and diamond earringsthat previously belonged toPrincess Dianaand pinned on the Irish Guards’gold shamrock brooch.

source: people.com