A 540-square-foot rental in Los Angeles has tropical peel-and-stick wallpaper, checkerboard floors, black cabinets, and a mix of thrifted midcentury furniture packed into one bedroom, one bathroom, and a kitchen you could cross in four steps. By any reasonable color count, it should feel chaotic. Instead, interior designer William Hutton, who lives there with his partner Kevan, describes a home where "there are so many colors within our home, but it's not overpowering," he told Architectural...