PAINT CAN change the whole scale and mood of a room," according to Foster Meagher, president of Meagher Design in Los Angeles.

Meagher, who is known in design circles for designing colorful Victorian homes in San Francisco, was in town recently on behalf of the National Paint and Coatings Association (NPCA).

Currently Meagher is working on a project called the "Bronx 2000." Without doing any reconstruction, Meagher has turned a decrepit building into a fantasy structure -- bright red, blue and green buildings with stylish signs and attractive lampposts and flagpoles outside. He has used colors that blend with the community, highlighting them with bold color schemes, but has kept the building intact. Meagher also is talking with the New York City government about painting the city's graffiti-covered subways.

Meagher has advice to hand down on smaller projects, closer to home.

For redesign inside the house, Meagher suggests taking into consideration how many people use a room, what the room will be used for and the age of the users.

"Adolescents," he said, "are very responsive to primary colors. If you don't have to worry about children, however, you can be more versatile.

"Traditional uses of rooms in a house can and should be changed. The living room doesn't always have to be the living room -- especially once the kids are grown.

"Wallpaper," he believes, "is slowly being replaced by paint. Artwork is shown to its best advantage when hung on a painted wall. Wallpaper takes away from the artwork, forcing the artwork to compete. Wallpaper has also become more expensive than paint.

"Don't stretch a can of paint further than its label suggests," said Meagher. To be sure you have the same shade of paint on all walls, buy enough to do the entire job. Paint batches can vary.

Meagher and the NPCA have other helpful suggestions on painting interiors:

* COLOR SELECTION . . . Select colors to complement the mood you want to make; consider the floor covering, upholstery, drapery fabric and accessories. Take into consideration how much light the colors will receive. Your own wardrobe, an oriental rug or your favorite painting will suggest colors.

Meagher notes that we make color decisions every day when we dress. "We choose colors that coordinate or contrast with one another. The same decisions go into paint selection."

Once a dominant color has been selected, add other colors in unequal amounts. Maintain a certain amount of color continuity throughout the home.

When studying paint chips, mask the other colors on the same paint card so your eye will see only one color and not blend the colors together. Prop them up vertically as they will appear on the wall.

* PAINT TYPES . . . Water-based latex paints are good indoors. They are washable -- a help where there are children. They are not flammable and have a mild odor. Latex has more clarity in color than oil paints -- particularly in deeper hues. Oil-based or alkyd paints have a high gloss. Since turpentine or mineral spirits is needed to clean them, oil paint is preferred for kitchens and bathrooms, where frequent cleaning might wear down a latex paint.

Finishes range from flat to glossy. Most oil paints have glossy finishes. The type you choose depends on the look you're after.

* PREPARATION . . . Before painting, check plaster walls for cracks. Fill in hairline cracks with spackling material, larger cracks with special patching plaster. Clean the surface to remove dirt and flaking paint. Remove all hardware from doors and windows and lighting fixtures.

Prime bare or new surfaces with a primer suggested by the label of the top coat or with the top coat itself. Cover floor and furniture with dropcloths or sheets. Try to clean up splatters as you go along. If using flammable, solvent-thinned paints, be sure all pilot lights are turned off.

* PAINTING . . . When painting ceilings, work across the width rather than the length to prevent one lap from drying before the next lap is painted. Paint in strips about two feet wide, slightly overlapping each strip.

When painting walls, begin at the upper left-hand corner if you are right-handed and at the upper right-hand corner if you are left-handed. Work down, toward the floor. When using a roller, paint the outside edges with a brush for a neater job.

For woodwork, use a round, one-inch brush for horizontal and vertical window sashes. Use a two- to three-inch brush for the rest of the trim work around the house.

* APPLICATORS.. Natural bristle brushes are good for oil paints and finishes such as varnish, enamel and shellac. They shouldn't be used with latex paints with smooth surfaces. Nylon brushes are more abrasive than polyester and work best on latex painted rough surfaces.

MEAGHER'S "BRONX 2000".

Meagher says that in painting stores it's important to do the entire building not just the store front. "Signs are important", he notes "but the words themselve sneedn't be so large to attract attention. Instead they should blend in with the total look of the building. It's that look that should lure prospective customers."

Meagher is optimistic. He believes that his buildings will be left free of the graffitti that plagues everything in the area. "People respect good looking buildings, he says."

Every city says Meeagher has its "own"colors depending on the angle of the sun and whether the area experiences seasons. In San Francisco, Meagher used pinks and blues on his Victorian Houses; in Seattle, crisp cool colors, blues, grays look best; here in Washington, sats Meagher, colonial colors are proper-whites, blues, reds in the Bronx, he used greens and whites.