For two decades, the hilltop house overlooking Alexandria’s Belle Haven Country Club provided a proper traditional setting for the politically well connected. The 1936 home was formerly owned by Margaret and Marvin Bush, the youngest brother of President George W. Bush and co-founder of Winston Partners, an investment firm based in Arlington.

In December 2010, the couple sold the 1.4-acre property for $2.5 million with the help of real estate agent Jeanne Warner, the wife of former senator John Warner (R-Va.), and purchased a condominium in Rosslyn’s Turnberry Tower.

Out went the Bushes’ beige sofas, Queen Anne-inspired dining set and comfy club chairs from rooms decorated in the staid, old-school style.

In came a refreshed style, expressed through energetic combinations of geometric patterns and cheerful colors. The new owners of the house prefer their traditional furnishings be shaken, not stirred, with a twist of contemporary design thrown into the mix.

A home always takes on the personality of its owners and, in this case, the genteel house with its long veranda has been transformed from what might be described as old Washington — one tied to politics and the money that comes directly from it — to a new symbol of what Washington aspires to be — more cosmopolitan and trendy.

The new homeowners are Larry and Stephanie Stack and their two sons, Leighton, 8, and Everett, 5. Stephanie Stack stands out in a political town as a singer of adult contemporary tunes whose work is attracting notice. Her 2011 album, “I Can,” was nominated this year by the Washington Area Music Association for a Wammie award in the best pop recording category. Husband Larry Stack, who works for a global consulting firm, helps manage his wife’s career.

In remodeling, the couple’s first move was to get rid of the mural commissioned by the Bushes for the foyer. The hand-painted scenes of a harbor, vine-covered arbor and dappled sky have been covered over by trellis-patterned wallpaper, a hot design trend these days, to lighten the large vestibule.

Gold-trimmed moldings and mantels in the living and dining rooms have been repainted in Benjamin Moore’s White Dove and the subdued color palette of the Bush era replaced with brighter fabrics and finishes.

Before buying the property, the Stacks had been living in the Belle Haven neighborhood in a recently completed builder home but yearned for the charm of historic architecture. “We had always admired the Bushes’ house,” Stephanie Stack says. “What impressed me was the grand veranda along the front and all the details inside, the exquisite moldings and 10-foot ceilings.”

The couple appreciated that the older home had eight fireplaces — four gas-fueled hearths on the main level and four wood-burning hearths on the second floor, including one in the master bathroom.

Even before signing the contract on the house, Stephanie Stack had begun looking online for an interior designer to put a new stamp on the old rooms.“We wanted to keep the integrity of the house but modernize it with something fresh, young and happy,” she says.

Stack’s search led her to Bethesda-based Kelley Proxmire, a seasoned decorator of show houses (20 of them since 2001) as well as real homes, who is known for lively contrasts of hues and patterns. “I like that she mixes antiques and contemporary pieces, and knows how to give impact to a room through pops of color,” the homeowner says.

The designer, who is married to financial analyst Teddy Proxmire, son of late senator William Proxmire (D-Wis.), started the project by consulting her favorite bin of fabrics. The starting point of her design became the diamond-patterned silk now covering a chair in the Stacks’ living room. “They loved the colors, so I pulled the same shades of green, blue and white, and added brown.”

Proxmire applied this palette to create a color flow from one room to the next, since the ground-floor spaces open directly to one another. “That helps to make the entire interior feel unified,” she says. Light blue ceilings in the adjoining rooms mimic the sky visible through the windows.

The homeowners tackled the decorating in stages so that the foyer and living and dining rooms were remodeled last summer while they were vacationing in New England. That gave Proxmire and her team plenty of time to test certain aspects of the design. Before installing the large, lantern-style chandelier in the foyer, the designer had her assistant Emily Wallace swing on a rope hung from the rafters to make sure the structure could support the 55-plus-pound light fixture.

Like homeowners on HGTV, the Stacks returned for the “reveal” after their vacation and found their bare living spaces filled with new furniture and accessories.“I opened the door and my jaw dropped,” Stephanie Stack recalls. “I was stunned by the dramatic transformation.” Only a few of the couple’s previous belongings remained, including a French chest and a curio table.

Now the living room serves as a stylish salon for music and entertaining. Its white sofas and chairs are paired with a Lucite coffee table and a baby grand piano for accompaniment to Stephanie Stack’s singing. A blue-spotted rug is bordered in the same apple green color of the drapes.

“It provides a place for the adults to go and have quiet time away from the children,” Larry Stack says. The couple plans to hold a party in the space to celebrate the release of Stephanie Stack’s newly recorded single and video, “What I’d Rather Do.

In the dining room, an impressive contemporary chandelier made of interlocking glass horseshoes hangs over the walnut table used for family meals and holiday dinners. Chairs are upholstered in textured vinyl that can be wiped clean and a dark brown carpet hides any crumbs. “I wanted to be practical because of the family’s two boys,” Proxmire says. “There’s nothing worse than not being able to be a kid in your own home.”

Next to the dining space, the family room was remodeled in time for this past Christmas with the same concern for practicality. Chairs and window seats are covered in durable fabrics meant for outdoor furniture; the colors match the yellow paint inside the bookshelves between the tall windows.

A zebra-patterned ottoman next to the sofa serves as a coffee table and, occasionally, a trampoline for the Stacks’ youngest son. “This is where the family gathers every Friday night,” Larry Stack says. “It’s a great place to play games, do puzzles and watch movies.”

The sun room at the far end of the family room was created by the Bushes when they enclosed a porch. This formerly white chamber has been recast as a “man cave” with chocolate brown walls and a sitting area for watching the flat-screen TV above the fireplace mantel. “Kelley understands that a man needs a TV, even if it is covered in a two-way mirror and enclosed in a frame,” Larry Stack says with a laugh.

For the singer, the joy of her newly decorated house stems from the unusual details in even its smallest spaces. She compares the vestibule between the family and sun rooms to “a jewel box” in pointing to its padded fabric walls, as soft to the touch as a seat cushion. “What I love about the design of this house are all these unexpected touches,” she says.

Deborah K. Dietsch is a freelance writer.