William Morris, founding father of the 19th-century Arts and Crafts movement in England, is famous for teaching, "Have nothing in your houses that you do not know to be useful or believe to be beautiful."

He could have been describing a modern-day decorator show house. These seasonal showcases of interior design convey the glamorous side of the design business. But beneath the layers of imported tufted velvet, simple ideas reside.

Even decorators run to Pottery Barn for place mats.

In other words, you don't have to own a palace or possess a fortune to take something home. The Capital Design House, a decorating event that opened this week in McLean, provides such user-friendly ideas as these:

* Color as a "neutral": The late 20th-century trend to minimalism has given rise to all-white rooms, or beige ones where white just won't do. But Washington interior decorator Barry Dixon has employed a bright yellow palette throughout the first floor of the house. Though brimming with color, the walls act as a neutral background for furnishings. Style note: walls and window treatments should blend.

* Plain paint: The color used in this house has come ready-mixed, straight from a can from Farrow & Ball, a British manufacturer and supplier to stately homes for 300 years. ("OctagonYellow" is named for a color used in the restoration of an Octagon Room at the Assembly Rooms in the city of Bath.) At $45 a gallon, Farrow & Ball is still a designer paint. And its availability remains limited to professional sources ( in this area through J. Lambeth showroom at the Washington Design Center). But it's a leap in the direction of easier application. Dixon says light colors sometimes require just one coat. (His favorite is Lime White in a room with natural stone.)

Farrow & Ball points out its paint was used in the TV production of "Brideshead Revisited" as well as "Moll Flanders" (the inns, not the dungeon she fell into).

* Natural materials: At the end of the millennium, Dixon is urging fusion with nature through the liberal use of linen, stone, wood. "I think people are interested in honesty," he says. "Certainly the American people are interested in honesty after all that's gone on here."

* Going with the flow: Dixon avoids thresholds. He believes they only create barriers to the proper visual flow.

* Custom look for less: Teri Kreitzer, who works for Barry Dixon Inc., suggests that the kind of custom edging that makes designer draperies special can be applied to less costly fabrics. All that's required is talent at a sewing machine.

The window treatments at the design house are often banded with extravagant materials. But they tend to be simple, clip-ring-on-a-rod styles, which can be duplicated at home.

* Shopping for character: While decorators cull high-end markets for finery, flea markets will provide just as much cachet in an average setting. The point is to mix old with new to give a room character.

The Capital Design House, sponsored by Southern Accents magazine, runs through Dec. 5, and benefits the Children's National Medical Center. Visiting hours are Wednesday to Friday, 10 a.m. to 4 p.m.; Saturdays, 10 a.m. to 6 p.m.; Sundays, 1 to 6 p.m. Tickets: $20. Shuttles provide transportation from McLean Presbyterian Church, 1020 Balls Hill Rd. For details, call 888-212-7050.