The state visit began with the first couple squinting into the sunlight — his face resting in a scowl, her eyes nearly lost in the dark shadows of her lashes. It ended with them standing stiffly in the twilight as guests arrived for dinner. His mouth turned down. Her face without affect.

In the morning, President Trump and first lady Melania Trump walked out of the White House holding hands and took their place overlooking the South Lawn. The jacket of his navy suit was buttoned; a tiny American flag was pinned to his lapel. She wore a powder blue dress with balloon sleeves from the Australian brand Scanlan Theodore. It was a gracious nod to her guests.

Her posture was as rigid as his as they stood shoulder-to-shoulder awaiting the arrival of the Australian Prime Minister Scott Morrison and his wife, Jenny. The president did not turn to chat with his wife; she did not turn toward him. They did not smile. She took a deep breath.

When the Morrisons stepped out of their motorcade, the rigidity relaxed. The Australians ambled forward. The president chuckled. The first lady bent down from atop her skyscraper snake pumps to greet Jenny Morrison with a kiss. Mrs. Trump smiled.

This was the second state visit the Trumps have hosted. The first, in April 2018, was in honor of France and for that day’s arrival ceremony, the first lady paired her white Michael Kors suit with a matching hat commissioned by her stylist Hervé Pierre, who had also designed her inaugural gown. That hat was quite a spectacle; it was both dramatic and protective, its brim serving as a kind of force field to ward off unwanted displays of affection.

She wore nothing quite so theatrical Friday morning. Her blue dress, which sells for $800 on the Scanlan Theodore website, was quite workmanlike in its simplicity. Crafted from crepe knit, it’s the sort of dress a professional woman might pack into her carry-on confident that it wouldn’t wrinkle.

For the evening’s dinner in the Rose Garden, Mrs. Trump wore a sea foam silk chiffon gown with waterfall ruffles from the New York-based design house J. Mendel. The dress had an ethereal quality as it fluttered in the September air. The president’s tuxedo jacket was maddeningly unbuttoned.

Mrs. Trump has worn gowns from J. Mendel before, most notably last year when she chose a yellow pleated dress with a cape-like train for a visit to Blenheim Palace in Oxfordshire. The designs, by the brand’s creative director Gilles Mendel, tend to be classically feminine, but with a hint of drama and Old World panache. They are dignified.

This was not a one-of-a-kind creation from Mendel but rather a dress that was part of his spring 2019 collection and one that could be purchased off the rack at Bergdorf Goodman for $5,990. (By the time Mrs. Trump debuted it, the dress was marked down to a mere $1,497 and came with free shipping. And before the evening ended, it was sold out. )

There’s a kind of brave and, perhaps cocky, transparency in choosing a dress that is available off the rack. The cost of it is right there for anyone who wishes to know — and, undoubtedly, judge. First ladies are responsible for the cost of their own wardrobe. But even if they’re not footing the bill, taxpayers have always deemed the first lady’s public wardrobe to be a public matter. The cost is a moral test and frugality is next to godliness.

One could also argue that there’s something mildly accessible about an off-the-rack frock — no matter the cost. If you’ve got the money, it can be yours. No special connection or status is required. There is one-percenter camaraderie in Mrs. Trump’s pale green confection that nods ever so slightly to the national colors of Australia, which are green and gold.

There is, of course, the risk that a guest might turn up wearing the same evening gown, which is precisely what happened to first lady Laura Bush when she and President Bush hosted a White House reception for the Kennedy Center Honors in 2006. Mrs. Bush was one of four women wearing the same $8,500 red Oscar de la Renta dress. (Mrs. Bush ultimately dashed to the residence and changed.)

The price tag can often distract from fashion’s distinctive currency: its ability to speak eloquently about culture, identity and status. The president’s tuxedo — classic but unbuttoned — suggests that he will play to traditions at least for the evening but he’s not fully committed to the pesky details and niceties.

What does the first lady’s choice of attire say on these grand occasions?

Mrs. Trump’s clothes have sometimes spoken with quiet respect. She wore Chanel haute couture when she welcomed French president Emmanuel Macron and his wife Brigitte to the White House for the state dinner last year. Mrs. Trump has also fired off a vitriolic message of disregard with a Zara jacket graffitied with “I Really Don’t Care. Do U?” But mostly, her clothes simply say, “And so, I am here.”

They announce that she is standing in the role. And when duty calls, she will take a deep breath. And be present.