Heidi Caillier loves to play with the grid, laying down graphic carpets to ground confident layers of geometric, plaid, patchwork and floral patterns, along with curvaceous vintage and custom furniture. To give a builder’s spec house in the Hamptons a charming Cotswold-cottage glow-up, the self-taught Washington state–based interior designer “added ceiling beams and paneled walls and drenched the principal bedroom in Benjamin Moore’s Quietly Violet, which,” she explains, “cocoons and sets the calming tone of the entire space.” A fanciful Stephen White Luminessence light sculpture and a Bradley Sabin installation of ceramic blossoms strike a romantic note and serve as counterpoints to the free-edge custom headboard, BDDW nightstands and vintage Boréns Borås sconces, sourced from 1stDibs. In a corner, between two windows offering expansive views of the garden, Caillier added a Josef Frank floor lamp with a tripod base and a 19th-century English work stool on either side of a shapely Ib Madsen and Acton Schubell Pragh armchair found on 1stDibs.  “We covered it in this pretty Pierre Frey pink,” Caillier says. “It’s the perfect piece for this bedroom and such an ideal place to read and relax.”