You’d never suspect, considering the black, white, and gray work attire favored by a certain Chicago-area marketing professional, that her Hinsdale home is as full of color as it is—lemony yellow, peachy pink, vibrant turquoise, and more.

“I typically wear black pants to work,” says this mother of three children, ages 3, 5, and 8. “And you’d never catch me changing out my necklace,” she adds, laughing.

Enter designer Summer Thornton of Lincoln Park’s Summer Thornton Design. After a thorough online search for a compatible aesthetic partner for this project, the homeowner hired Thornton to help her move beyond the familiar territory of neutrals.

Thornton’s marching orders: to create a lighthearted, kid-friendly retreat in the new-construction, four-bedroom Hinsdale home, which the family moved into in 2010. It would be a sharp contrast to the Chicago condo they had left behind, which was done up—predictably—in black, white, and gray.

The homeowner “used the word ‘happy’ a lot,” says Thornton. “She wanted it to be a cheerful space, above all.” The designer worked on the rooms one at a time over the next few years, starting with the first-floor great room and proceeding to the master bedroom upstairs, the most recent project. Tackling the rooms one by one kept the project’s cost and pace manageable for the pragmatic client.

Smart handling of bold color throughout the house ties it all together. A vivid, almost acidic yellow on drapes and an upholstered head-board in the master bedroom is tempered by sophisticated elements—monogrammed white bedding and mirrored nightstands, for example.

In the great room, neutral wall color and some pieces the family already owned, including a gray sofa and light brown chairs, balance vibrant blues, corals, and oranges in artwork and accessories. Those include silhouettes of the children created by artist Julie Foley—two of them rendered in turquoise—and a humorous pair of prints with playing-card themes by Danish artist Bjorn Wiinblad.

In the dining room, a vintage 1950s French chandelier purchased from New York–based Buck House makes another splash of color. The round table underneath, by Chicago furniture-maker Aaron Bladon, is a more serious counterpoint.

Striking a balance between neutral and and not, serious and whimsical, helps keep the home’s overall tone playful without being childish.

At present, with a few more rooms left to redo, the home-owner’s favorite space is also the most daring. The first-floor den, cloaked in a moody blue lacquer (including ceiling coffers and a wall-spanning desk) is used as a place for evening reading and relaxation. Its location, closed off from the rest of the first floor with French doors, allowed even more freedom to experiment with color.

“I wanted someone to push me outside my comfort zone,” the homeowner says of her partnership with Thornton. “Otherwise, I’d just have another house of black, white, and gray.”