Even when Jillian and Tim Sassone lived in Brooklyn, the city of Palm Springs, Calif., had a special place in their hearts. Enamored of the area’s mix of desert, mountains and midcentury modern design, they held their wedding there in 2010.

So when they moved to the San Diego area about a year later, they continued to make regular visits. “We were going out to the desert four or five times a year,” said Mr. Sassone, 40, who owns the jewelry company Marrow Fine with Ms. Sassone, 41, the company’s lead designer.

Eventually, they began looking for a Palm Springs weekend house to buy. But finding something they liked was difficult. “A lot of what we saw needed so much work that we just transitioned to looking at land,” Mr. Sassone said, with the idea that they would be better off building a house from the ground up.

They began talking to architects and were close to buying an empty lot when their real estate agent mentioned a property that was about to be listed for sale: a 1957 house by the celebrated modernist architect Donald Wexler in Rancho Mirage, a city about 10 miles southeast of Palm Springs.

“He was, like, ‘The floor plan is exactly where you’re trying to go, only it’s pretty much done,’” Mr. Sassone said. “We were excited by the idea of a Wexler,” he added, as well as the possibility of avoiding a multiyear construction project.

Their agent arranged for them to see the house before the sales listing went live. What they found was a spotless three-bedroom, 3,340-square-foot house that had been renovated by a previous owner. Some elements didn’t gibe with their personal style, but they decided they could dramatically change the look of the primary living spaces and yard while keeping the kitchen, three bathrooms and overall architecture largely intact.

The Sassones made a quick offer to secure the house before others saw it and closed in August 2019, for $1.379 million. Then they called Barbara Rourke and Jason St John, the founders of the Los Angeles interior design firm Bells & Whistles, for help.

Ms. Rourke and Mr. St John had recently completed Marrow Fine’s colorful store in San Diego — defined by arches, scallops and shades of pink, blue and green — and were thrilled by the opportunity.

“It was a beautiful Wexler,” Mr. St John said. “For us, it was one of those dream projects.”

Everyone involved was committed to preserving the original architecture, but neither the owners nor the designers were interested in replicating a 1950s interior, he said.

“When someone says ‘modern,’ what does that mean?” Mr. St John asked. “It can mean so many different things. To us, modern is pushing the edge of what’s cool, what’s popular and what’s trendy, and really going to the very edge.”

Knowing that the Sassones intended to use the house not only for relaxing weekends but also as a location for photo shoots and events for their business, the designers were keen to create Instagrammable details.

“We definitely approached it as: ‘What’s going to look good in a photograph and what’s going to be an impactful design?’” Ms. Rourke said. “Most of what we did was just adding interior elements and trying to make a big wow with things that weren’t permanent and didn’t alter the structure.”

Repeating many of the shapes and colors found in Marrow Fine’s store, the designers added a curvaceous, coral-colored velvet sectional sofa in the living room atop a shaggy flokati rug, as well as a custom bar cabinet with a fluted blue front. In the dining room, they hung gold-plated pendant lamps with green fringe above a long table surrounded by cylindrical pink chairs. For each of the bedrooms, they chose a graphic wallpaper.

The Sassones also involved their daughters, Gemma, 8, and August, 6, in the design process. When the girls asked for a disco ball, Bells & Whistles mounted one measuring four feet in diameter in an atrium adjacent to the foyer and living room.

“The kids get to have dance parties, and it just lights up the whole living room,” Mr. Sassone said.

But the most attention-grabbing feature is outside, where they commissioned Alex Proba, of New York-based Studio Proba, to paint the inside of the pool with large free-form shapes in a multitude of colors.

When Bells & Whistles proposed the idea, “we were all about it,” Ms. Sassone said. “It’s such a rad idea and such a statement piece that’s so fun.” It was also a hit on Instagram when Ms. Proba posted images of the freshly completed work in early March.

When the pandemic struck, the Sassones moved into the house for a monthslong stay, overseeing finishing touches like the addition of an outdoor bocce court. They completed the renovation in May, after spending about $350,000.

Although they couldn’t have predicted the arrival of Covid-19 when they bought the house last summer, they are especially pleased with their decision not to build a home.

“It’s a three-year shortcut,” Ms. Sassone said. “We actually had a place to go, instead of a pile of rubble.”

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