It has also been noted that Kate's decision to wear white or cream at the christening of Prince George, Princess Charlotte, and now Prince Louis is due to the colours perfectly complementing the Royal christening gown, worn by all three children.
It's a festive week for the royal family.
As the Honorary Air Commandant of the organisation it's understood the Duchess wanted to be there for the day's events, regardless of officially being on maternity leave, following the birth of Prince Louis in April.
This was an opportunity to meet RAF veterans, serving personnel and their families.
And amid turmoil in the Cabinet and her Government, Mrs May delivered a reading at the service, Hebrews 11:32-12:2, with the head of the RAF Air Chief Marshal Sir Stephen Hillier also taking to the lectern.
City Player Urges Star Defender To Join Manchester United
Mahrez, 27, temporarily stopped training with Leicester after a move from the Foxes to City failed to materialise in January. I'm very confident in myself and I hope to help this team to improve".
Previously, it had been awarded to the top female cadet each year, but in 2015 the tradition was altered to give female cadets the same prize as male cadets, and the brooch was given to Kate.
After the service, the monarch, accompanied by Prince Charles, will present a new Queen's Colour to the RAF on the forecourt of Buckingham Palace and make a short speech.
Each appearance of the Duchess of Cambridge in public - another reason to discuss her attire.
The Duchess of Cambridge made a surprise appearance at the centenary celebrations for the Royal Air Force yesterday. We'll, of course, let you know if they do.
The flypast is set to feature aircraft including Puma and Chinook helicopters, a Lancaster, Spitfires, Hurricanes, the A400M Atlas, Tornados, Typhoons and the F-35 stealth fighter jets.