There is a new preppie look sweeping Washington.

It is the old preppie look.

(There is no new preppie look. Ever.)

But the important thing is that this look, which has made Washington the nonfashion capital of the country, this look is suddenly the look across the length and breadth of this land.

Solid-color shirts. Solid-color pants. (No style, thank you.) Alligators. Plain loafers. No fit. Heaven forbid a fit. It's all over. It's all around. It's in the air.

How many preppies does it take to buy a Ralph Lauren suit?

(Are you serious?)

Suddenly it's navy blazers, oxford button-down shirts, chino trousers, loafers and striped headbands -- longtime Washingtonian signatures -- on the cover of the new I. Magnin catalogue. At Bloomingdale's, it's "A Touch of Classics." At Garfinckel's, "The Prep Shop." At Woodies, it's the "Preppie Shop." At campus bookstores, it's the "Are You a Preppie?" poster.

"The Preppies are coming! The Preppies are coming!" said the poster at Neiman-Marcus. Yesterday was Preppie Day at the store, organized for the benefit of nonpreppy salespeople who were having trouble understanding the khakis and the madras that were inundating the store.

"It all started when one employe said she didn't know what a preppie was," says Neiman's Pam Porter. "And then a whole bunch of arguments started. So we decided to declare a day when everyone would come dressed to work as their own interpretations of preppie."

Porter dusted off her old Pappagallos, while bridal consultant Rosalie Harris came in a chiffon gown with white tennis hate, argyle socks and Izod belt.

"Everyone just looked marvelous," said public relations director Mary Ann Lundgren. "There were all these little seaters tied around their waists, initial rings, fraternity pins, penny loafers with pennies, ponytails, kilts . . ."

Several designers even co-opted the "preppie look" in Paris last week, particularly Marc Bohan at Christian Dior, whose models in one sequence wore striped blazers, button-down shirts and pleated skirts. And Paris boutiques are already showing Topsiders in every bright color.

But Washingtonians have never needed designers to show them how to dress "preppie." Says lobbyist Peter Kaplan, who got locked into the "preppie" style at the University of Virginia: "I'm traditional. I've been dressing one way all my life. And basically when I wear it out I get the same thing," says Kaplan, who shops mostly at Arthur Adler and Paul Stuart in New York.

"If I was skinny and French I might dress differently," he says.

The elements of this traditional, preppie look haven't changed much in 60 years according to Brooks Brothers Vice President Standley Jaffe. In the 1920s, Shetland sweaters were mostly earthen colors, and since then, Brooks has played with some style changes, but the basics have remained the same and remained the best sellers.

Jaffe thinks that designers ran out of fresh ideas when they started to hark back to his traditional look. "There's a limit to how much you can change things . . . the jacket needs two sleeves, the pants two legs," he says. "Things had gotten so outlandish that going back to tradition, good value, and not dull but good taste items seemed a natural."

Woodward & Lothrop Vice President Robert Friedman says the preppie look "simply started to happen" last fall as sales "took off" in Shetland sweaters, Oxford shirts and then lace-trimmed shirts. "It was partly college kids looking for a way to dress up without jeans," he says.

Designers are now revying up to cash in on the preppie look in an even bigger way for fall. Don Sayres, for example, will show a group of kilts, circle skirts and pleated skirts when his line opens next week. The Gator Hater

Another person cashing in on the preppie trend is Tom Shadyac, the creator of the "Are You a Preppie?" and the "Are You a Preppette?" posters. He calls himself a "Gator Hater who prefers Hawaiian shirts and dirty pants" and never heard of a preppie or a Lacoste alligator shirt until he hit the University of Virginia.

With business partner David Black, also a graduate of Jeb Stuart High School in Falls Church, he created the poster a year ago as a fund-raiser for his fraternity, Sigma Chi. So far they have sold 40,000 copies of the preppie version. The preppette poster is now being printed.

"The anti-preps loved it as much as the preps did," says Shadyac. "Not one preppie complained about it, because most of them thought, 'Hey, look at me, I'm on a poster.'"

That's typical of the preppie attitude, according to Shadyac. In addition to the obligatory navy "blah" blazer, upturned Izod collar, matching striped belt and watchband, baggy boxer shorts, and cuffs, or "rain gutter" pants Shadyac points out on his poster, there is a distinct preppie mode of behavior, precipitated by "an elite background and monogrammed toilet paper," he says.

That, he says, is what turns him off to preppies, not their "baggy plaid, lime, yellow or pink trousers (batteries not included); Topsider moccasins; tasseled loafers; pure wool socks or tweeds." Says Shadyac, 21: "If a preppie doesn't have that attitude, then I can get along with him."

Shadyac cannot understand why preppies have suddenly become chic. "I would imagine that it is the clothing that attaches a certain status symbol to you. It gives you a false air about you the people like -- everyone in prepdom is equal, you're equal to the next guy. Maybe it's the egalitarian ethic in America.

"University of Virginia is the home for prepdom in Virginia," says Shadyac, but Georgetown University Bookstore is our best-selling outlet in Washington."

Shadyac sees no end to the preppie trend. "There is an alarming increase in the number of prep cases reported," he says, noting the he has received requests for his poster from such unpreppie-like places as Mexico and Oklahoma. "I know there are English and French preppies, too," he says. "But I don't know how much the disease has spread in Europe."

Do Shadyac or Black have any preppie items tuck in the back of their closets? "Are you kidding" says Black. "Do you think I'd dress like that? Sometimes I do wear an alligator shirt, but Tom will always bite off the alligator." Prep for Success

The current crop of customers for things preppie is no longer limited to those with Ivy League ties and (blue) bloodlines. Elements of preppie have crept into the "dress for success" uniform. And customers looking for safe and familiar clothes that are not likely to go out of style have found these traditional classic items to their liking.

You have to look hard to find the changes in the styles at Pappagallo's, favorite shopping turf for prepettes. The 1980 Shetlands and Fair Isle sweaters may have buttons on the shoulder, and violet is about to be added to the color range of oxford shirts, and the hunting horn pin -- worn fraternity style -- is this year's alternative to the circle pin or safety pin. f

And, according to Jean Wong of Pappagallo's the new grosgrain headbands are a little bit narrower or braided.

What's not around at the moment are the shoes -- colored flats that used to come in yellow, green, pink or blue, once the store's best sellers. At the moment stacked heels dominate the store, but the old favorites are due in soon. m Spelling It Out

Preppie versus Preppy. You've seen it spelled both ways on store advertisements. Which is proper?

When Woodward & Lothrop decided to open a new junior shop stocking oxford shirts, madras jackets, Bermudas and all those necessary prep accessories, they had a big discussion on how to spell it -- with a "y" or an "ie." They finally decided to go with The Preppie Shop. "We turned to Erich Segal's 'Love Story' for the definitive answer," said a fashion coordinator. "We figured a Harvard preppie ought to know."