While Alec Holland, a New York City-based interior designer, has nothing against white walls and linen slip-covered sofas, his aesthetic is decidedly un-beige. To put it mildly, he adores color. “I wanted a fresh, clean feeling,” says Holland, who notes that here and there you’ll find white walls and even a piece or two of wicker furniture. “After all, it is a Hamptons home.”

Steffen Ringelmann, an interior designer and furniture builder who runs studio MTK, has a longstanding love of mid-century architecture and design. So when the new owners of a Leisurama, a married couple with one child, engaged him to decorate the place, he envisioned...