Ralph Lauren, who funded the current "Man and His Horse" exhibition at the Metropolitan Museum of Art's Costume Institute, cashed in on the idea Wednesday night with a fall collection for the rich, horsey set.

Perry Ellis jousted with harlequin diamonds, heraldic stripes and court jester tunics.

And Gloria Sachs, who develops the most luxurious printed silks in Italy, offered a mix of plaids and paisleys with a fresh slant, cut on the bias.

" 'Simple' is a magic word this season," Sachs said at the start of the show in her Seventh Avenue showroom this morning. "But simple clothes can be beautiful without being dull." Hers were just that.

But the designer most talked about by the buyers and press gathered here for the final lap of the fall fashion marathon was Albert Nipon, who was sentenced Wednesday to three years in jail for bribing Internal Revenue Service agents.

One executive, who asked not to be quoted, reported that a woman returned several Nipon dresses at the insistence of her husband, who had read of the trial. But Philip Miller, chairman of Marshall Field & Co., said, "I honestly don't think it will have a long-term effect on the business."

"He's made a mistake and he's sorry for it. It hasn't affected us till now and I don't think it will," said Norman Polonofsky of Bonwit Teller.

At least one store buyer described the problem at Nipon as "not in the personalities but in the pleats. The Nipon clothes are not very interesting at the moment."

But on the runways this week, retailers found some looks they expect will appeal to their customers.

Lauren, who has built his name and his fortune on the cachet of polo, has enriched his staple hacking jackets, jodhpurs and stock shirts with velvet and suede and Lurex. And he's got the most authentic of all the tapestry looks around in his sweaters with front panels that look like needlepoint and vests and jackets that look like they came off the walls of the Met.

He's on the same wavelength as Calvin Klein with his turtlenecks and trousers as an easy, modern way to dress. His turtlenecks are velvet, his favorite fabric for fall, and almost all of his trousers have stirrup bottoms. And, also like Klein's, his key accessories are crocodile belts and shoes.

Like Klein and Bill Blass, Lauren has slipped a logo back onto some of his top-price clothes. He embroiders a crest on jacket pockets and velvet slippers, and even tools it onto the pocket of a full-length leather coat.

From the equestrian crowd that gathered for the opening of the Costume Institute show, Lauren has taken the "pink" hunting jacket (truly a bright red with a black velvet collar), and interpreted it as a sweater. Another variation is the same look as a Chesterfield coat in bright red with black velvet collar and cuffs, perhaps the best coat in the collection.

Coats were also among the best pieces in Ellis' fall collection.

From draped, side-buttoned jackets to a lean rajah look to court jester patterns, the clothes are all lean and very short, worn with high suede boots that Ellis calls "wowo boots . . . because they come up to the wowo," his word for the hip.

As always, he succeeds brilliantly with his intarsia sweaters, which work well for both men and women. One tapestry sweater has a unicorn motif, others a Stradivarius violin (complete with label) and a comedy mask.

He is not so successful when he experiments with very serious clothes. In reviving the flounce, using it at the hem of a short skirt for day and evening, he has added a pointless frill. He is on much safer ground when he leaves things alone, as in his simple, lean, dark suits with crushed stand-up collars or long, slim black evening dresses.

If Ellis did not score with his court jester looks for women, it may be because he is putting more emphasis on his menswear, now more than 50 percent of his business. The oversized coats and jackets with very deep armholes and the injection of bright colors in shirts and sweaters -- including a revival of the mock-turtle -- worked handsomely.

Ellis started his menswear business because so many men wanted to wear the sweaters and shirts he made for women. This season, women will be happy to wear his clothes for men.

While most designers have been cautious in their use of color this season, Sachs has recolored her classics. The plaids in deep sienna tones are border-printed with paisley and glisten in lame' for evening.

She uses black and white as well this season, and has a new angle on them, cutting her skirts on the bias. And she has revived her reembroidered black velvet jackets for this fall, best of all when the embroidery is gold bullion. Those jackets look like money in the bank -- which is what this business is about, isn't it?