Why does Warren Robbins, founder of the Museum of African Art, wear a brown leather vest? Easy. He spilled something on his beige one and had it dyed brown.

Loraine Percy took her husband, Sen. Charles Percy (R-Ill.), behind the scenes at a Japanese Embassy gala dinner recently to introduce him to a favorite hairdresser. Suga from Bergdorf Goodman, who was preparing the coifs for the Hanae Mori fashion show. "He used to 'do' us all," said Mrs Percy, referring to Lorraine Cooper, Marie Harriman, Deeda Blair and Joan and Ethel Kennedy, as well as herself. Suga would fly to Washington for a day to take care of his local clientele before he linked up with Bergdorfs." While with Kenneth, he also styled Jackie Onassis' hair.

Suga, who believes that volume is more important than lenght of hair at the moment, ("Long hair is better for the young," he says) feels the frizz done with vigorous permanents or electric treatments isn't good for the hair. "Besides, when pin set or done with braids, it can be washed out easily," he added.

If Mrs Percy had any thought of Suga introducing the senator to a new hairstyle, the senator was not feeling very experimental. "I'm perfectly happy with my hair the way it is done at Headstart," he said.

"I've got my blue jeans on under my trousers to make a point," teased White House press spokesman Jody Powell at a press briefing the other day. Powell was responding to Sen. Edward W. Brooke's comment that, "When you go to the White House, the place looks physically dirty; people running around in jeans doesn't look right."

Powell challenged members of the press to name White House staffers who wear jeans in that building and only one name, that of speech writer Jim Fallows, was mentioned. According to a secretary in Fallows' office, Fallows, who was out of town, occasionally wears jeans on Saturdays.

Another Washington model has bit into the Big Apple. This time it's Alan Cephas, model and display director for Sweet Charlotte stores, who was spotted by designer Bill Blass and signed for his New York shows. He is pictured here in a burgundy corduroy double-breasted blazer and gray pants from the current Bill Blass collection.

"It is the kind of skirt you can wear if you ride a bike to a party," says Jenifer Bar-Lev, Israeli designer of the cotton knit skirt that can be worn (thanks to the strips attached at the sides) as a short jumpsuit, sarouel pants, even a strapless dress. Bar-Lev, 29, a Georgetown University graduate, stayed on in Washington after the Israel Bond Luncheon with her grandfather, philanthrophist Leopold Freudberg. She showed her five-way bicycle skirt with a "chewed up" undershirt, as she calls it. "It is sort of punk," she says. She was working on this look long before punk was known in Israel. Of the ragged-hemmed shirt with two straps on one shoulder, one on the other, she says, "I like it because it looks free." One current favorite hairstyle in Paris, braids, has long been popular in Israel. "Israeli girls wear braids alot," she says.

Does Macy's tell Gimbel's? Does Lord & Taylor tell Neiman-Marcus? Apparently so. Elaine Miller, wife of Philip Miller, president of Neiman-Marcus, has been named merchandise consultant for Lord & Taylor. She was sportswear buyer for Bloomingdale's until she moved to Dallas after her husband's recent appointment.

California Rep. Anthony Beilenson has introduced a bill to ban ivory and elephant product imports in the United States to discourage the killing of African elephants, the source for much of the ivory jewelry and artifacts sold here.

The African elephant is in serious danger of extinction, according to the Fund for Animals, both from the ivory trade and from human settlements and agricultural development encroaching on the elephant's habitat.

Tusks of a large bull elephant may weigh as much as 50 pounds. The average weight of tusks now being sold is less than 20 pounds, leading the Fund for Animals to conclude that most of the large animals have already been wiped out. The current price of ivory on the world market is $30 a pound, an increase of 1,000 per cent (from $280) since 1969. Such prices, of course, encourage poaching.

According to elephant expert Dr. Iain Douglas-Hamilton, author of "Among the Elephants," "The unofficial slaughter of elephants is probably worse than it has been since the turn of the century.

I. Magnin has taken advantage of its new Christmas catalog to rev up charge account customers for its White Flint debut in March. The current catalog mailed in the D.C. area includes a full-page pitch for customers to open charge accounts.

It may be the only fashion exhibit where the photographers are more familiar than the designers. The Brooklyn Museum yesterday opened a survey of fashion photography ranging from the classic works of photographers Richard Avedon, Irving Penn, Horst P. Horst and others, plus the more recent controversial efforts of Helmut Newton, Deborah Turberville and Chris von Wangemheim. Names not often associated with fashion photography like Edward Steichen, Diane Arbus, Man Ray and theatrical designer Cecil Beaton also have works in the show that spans a century of fashion photography. The show continues through Jan. 8.