The lowdown on all the royal fashion rules you didn’t know existed

The queen is always spotted in monochromatic vibrant colours—and for good reason. She wants the public to be able to see her through the crowd. In the 2016 documentary The Queen at 90, Sophie, Countess of Wessex (aka the queen's daughter-in-law) explained, "She needs to stand out for people to be able to say, 'I saw the queen'."

Her colourful ensembles are never complete without a hat in a matching hue, and that's because of a very old tradition that bars women from showing their hair. When she's not wearing a hat, she usually ties a scarf around her head. While modernisation has eased up the rule, the rest of the royal family are still required to wear fascinators to all formal events.

Just like wedding rings, tiaras are only reserved for royal brides and those who are married. According to Geoffrey Munn, the author of Tiaras: A History of Splendour, "it signals the crowning of love and the loss of innocence to marriage." Kate Middleton, Meghan Markle, and Princess Eugenie all wore their first tiara on their wedding day.

While hats are a must at all formal events during the day, they can only be worn until 6pm. The reason is simple: That's when the tiaras come out to play—for those who are married, that is.

Royals are only allowed to wear all-black looks on specific occasions such as Remembrance Day, but they're required to pack a full-black outfit while travelling in case of emergency. This was a rule set by Queen Elizabeth who was forced to stay on the plane until a black outfit was delivered to her when her father, King George VI, passed away while she was on a trip to Kenya.

Royal brides may have flexibility when it comes to the style of their wedding dress, but the Queen has the final say on the design. Kate Middleton and Meghan Markle both reportedly got their grandmother-in-law's approval during and after their gowns were completed.

Cleavage is a no-go when it comes to the royal family, although Princess Diana is known to break the rules. She was known to hold her clutches—or what Anya Hindmarch told The Telegraph, "cleavage bags"—to shield her chest when she stepped out of cars.

No matter how warm or how uncomfortable it is, the royals never take off their coats in public because it's deemed unladylike to undress in public.

All royals have to look prim and proper on all occasions, and when they make their public appearances, their dresses or skirts can never be more than three or four inches above the knees.

This is not exactly a rule, but the royals are encouraged to pay homage to the country they're visiting with their fashion choices. Kate Middleton wore a dress by Australian designer Zimmermann during her trip to Australia; a royal blue Kurta by Maheen Khan during her second day in Pakistan; and an all-green outfit when she arrived in Ireland.

You may have noticed Prince George and Prince Louis have mostly been spotted in shorts, and that's because of a tradition that dates back to the 16^th century. Young boys from the upper class, aristocracy, and royal families are encouraged to only wear shorts until they're about eight years old.