As a longtime royal reporter, I can think of one obvious reason for old-fashioned, color-coordinated, and repeated clothing: security.

Think about it. What image do you see in your head when you think about the Cambridge children? Old-fashioned shoes and knee socks, floral dresses, polo shirts, and now, for George, suits. Not exactly the sort of thing a child would wear on a playground or a trip to the grocery store with their parents. The Cambridges have been ferocious in guarding their children’s privacy. But, every so often, paparazzi photos emerge online that were clearly taken in what the Cambridge family believed was a private moment. In these images, the little princes and princess are dressed “normally,” in casual t-shirts, shorts, and, in one case, a soccer/football uniform.

But beyond practical reasons, there appears to be a deliberate sartorial strategy at work here. What might it be? To answer this, I talked to Susan Kelley, the royal fashion chronicler behind the websites What Kate Wore and What Kate’s Kids Wore. These websites have been cited in news outlets around the world for their ability to identify royal clothing quickly.

One of the first things Kelley noted in the interview was the Cambridges’ preference for the color blue. “It’s the color that reads easiest for people,” she said. “It’s the most favorable to the eye. I learned that working on television sets and with graphic designers.” (Note: Kelley is correct; you can read more about the use of blue in television here and here.)

“Both Kate and William are savvy and sensitive to the media,” she said. “It’s very smart to have [the children] repeat outfits and wear the same things [and focus on] simple, solid-color basics. … You don’t want what they’re wearing to be distracting from the moment, but what they wear is going to be important — and it needs to be appropriate.”

Kelley noted the importance of the traditional shots of the royal family on the Buckingham Palace balcony and how those occasions are when you tend to see old outfits again. “I think part of the rationale behind that is the continuity of the monarchy and the future kings,” she said. “It speaks to tradition, it speaks to frugality, and it speaks to the sentimental love from people who have been fond of William and Harry since they were children and watched them grow up.”

As for the clothing itself, Kelley said that, based on her longtime observations, “Kate tries to keep things ‘noncommercial,’ understated, and traditional.” She noted the many hand-me-downs in the family, such as a blue sweater that was seen first on George, and then twice on Charlotte. “Lots of heritage brands, British brands, all-natural fibers… styles that are made by hand by small businesses or independent seamstresses.”