Given the news that Prince William has been made colonel of the Irish Guards, a new sartorial question is raised: Will he get married in red?
The iconic garb of the Irish Guards consists of a scarlet tunic and a bearskin, which is a tall fur cap.
Formed in 1900 by order of Queen Victoria, the Irish Guards is a regiment steeped in history. The way to tell them from the other five regiments of the Foot Guards is by the spacing of their buttons, which are arranged in groups of four.
This is because they were the fourth Foot Guards regiment to be founded.
The queen gave her formal approval to her grandson's new appointment, and it was announced by her press secretary Thursday.
This is William's first honorary appointment in the Army, and he will be the Irish Guards' first royal colonel. The queen is colonel-in-chief.
Duties for the soon-to-be-married prince will include taking a close interest in the lives and activities of the regiment's personnel. Normally based in Victoria Barracks, Windsor, the regiment is deployed to Afghanistan.
William, 28, already holds honorary ranks in the Royal Air Force and Royal Navy.
Such history and tradition go hand-in-hand with customs and routine, which can sometimes we interpreted as "rules."
And the best place to start for tips on the proper etiquette is Burke's Peerage & Gentry.
"Etiquette is, in short, knowing what to do at the right time and knowing what to say at the right time," editor William Borthwick told ABC News.
So, it's not so much rules as hints to help you out. After all, how many people know exactly how to address the queen, or Kate Middleton, for that matter.
"She will immediately become Her Royal Highness Princess William of Wales," Borthwick said of Middleton's change of name after marriage.
And her first name?
"I think 'Catherine' is probably more fit for a royal princess of the British royal family and future queen," he said.
That Middleton is to marry into the royal family is, indeed, a break with traditional "royal rules."
A generation ago, someone like Middleton would never have had a chance to marry a prince.
"Well, no, she would have been called a commoner," Marina Hyde of the Guardian newspaper told ABC News, "and he'd have had to go looking for some nice princess of Denmark."
But William has chosen Middleton, whose mother was a flight attendant.
The Self-Made Middletons
Sticklers for tradition have criticized Carole Middleton, in particular, for a faux pas at William's military graduation: She was reportedly chewing gum.
"I do think people have been terrifically, really unappealingly and horribly snobby about it," journalist Hyde said.
Middleton's parents made their money selling party paraphernalia, a break from the children of aristocratic families who have previously married into the British royal family.
"They're self-made millionaires," historian Robert Lacey said, "and we should all be celebrating that."