Beyond its pristine beaches and bustling downtown, there’s a decidedly sylvan side to the town of Southampton. Take the wooded hamlet of North Sea, whose secluded plots lured a young, New York City-based family seeking a peaceful getaway for weekends, holidays and long summer sojourns.

Though the location itself was worthy of a fairy tale, the current state of the early-2000s home was decidedly less so. “The flow was discombobulated and the previous owners—a large family—had lived there for many years, so it had some pretty obvious wear and tear,” recalls Ariel Okin, whom the clients enthusiastically enlisted to lead the redesign while they were closing on the property. “Our goal was to create a modern, whimsical home that would feel light, open, family-friendly and personal,” the designer shares. “It was also really important that it be like a retreat and reprieve from the world.”

In collaboration with general contractor Neal Owen, Okin kicked off the brief with a cosmetic renovation to brighten and enhance the architectural interiors. “Part of the magic in working on this house was clearing away the existing decorative finishes so that we could see it with fresh eyes,” she recalls. That meant gut renovations rendered in timeless Carrara marble and polished nickel for every bathroom, entirely new warm wood flooring throughout the house, and fresh white paint or pale, subtly patterned papers to impart an airy crispness to the walls.

One existing feature that was carefully retained, however, was a pair of funky bamboo atriums in the foyer, the effect of which evokes entering a tree house. It was this very spirit Okin had in mind for the interiors already, since virtually all of the windows frame lush foliage. After all, what’s a more escapist design trope than a tree house? But this iteration would be less Swiss Family Robinson and more California-meets-the Hamptons, in keeping with her clients’ contemporary-leaning tastes.

“The house is mostly glass and has amazing vistas of the woods from almost every corner,” notes Okin. “We decided to play up the views by incorporating beautiful drapery to draw the eye to the windows and ceiling height.” After highlighting the natural setting, next, he designer endeavored to bring the outdoor bounty inside with a happy-hued palette derived from the surroundings. “The colors were inspired by the Hamptons itself,” she explains. “But it’s not too on-the-nose beachy. There’s ice blue, pool blue, aquamarine, yellow for some sunshine and green as a clarifier with different shades, from pale to spruce.”

Reinforcing the tree house ethos in a subtle fashion while bringing an element of California Zen, “the grounding constant in each room is a great neutral” Okin notes. Take the dining room, which is anchored by a wall of bespoke cerused-wood built-in bars with brass and mirror details. Together with an eclectic mélange of textiles, the space feels unexpected despite its classic Hamptons palette. “The blue-and-white color scheme in the dining room is traditional in a sense, but turned on its head to feel more boho thanks to the patterns we used,” explains the designer. In the primary bedroom—a serene yet richly layered retreat awash in shades of green, burgundy and brown—a faux bois wallpaper achieves a similar anchoring effect. Even the formal living room, which touts the full rainbow of Okin’s joyful palette, finds its organic counterpart with a base of creamy, nubby upholstery fabrics.

Okin’s chorus of greens, blues and yellows converges again in the breakfast area, a charming nook the designer carved out to enjoy views of the outdoor lounge area and pool. There, she paired a long, cushioned banquette with a shapely tulip table and mismatched dining chairs. “The multicolor chairs are so fun and different, and felt perfect for these clients,” the designer says. And for times when the homeowners seek a warmer dose of color, an upstairs office draped in exuberant textiles in shades of tangerine is as energizing as an Aperol Spritz—and just as enticing on a summer day.

In all, it’s a home that elicits a smile—and this is exactly what the designer wanted to gift her clients and their many-numbered visitors. “I hope the house has a happy, inviting effortlessness,” Okin reflects, adding, “and I hope that energy becomes infectious!”