In a white box, three-bedroom pied-a-terre in New York City’s Chelsea neighborhood, we chose a sophisticated color palette of black, white, cognac and navy. We added color and warmth using wallcoverings and sleek furnishings, making this modern open-plan layout feel like home away from home for a Houston couple who often visit their adult children. A vintage black Marquina marble table is surrounded by chairs upholstered in a diagonal racer-stripe, a nod to the family’s sporty lifestyle.