Yves Saint Laurent blew the fuse on the Paris collections yesterday. Three times the lights went out during his show, undoubtedly caused by the heavy load of television cameras filming every inch of models in the grand finale show of the week-long presentation of French ready-to-wear for spring.

The 1,500 or more buyers and members of the press remained calm, waiting to see more of the familiar YSL classics freshened up this year with splashes of gold and bright colors, new sleeve shapes and hip treatments that will themselves become classics before long.

Saint Laurent also defused some of the excitement of the other designer shows. In the past, he has experimented with pants shapes, including zoaves (billowy, knee-length harem pants) and knickers. But this year he has gone back to the classic trouser. Of course, there are a few of the others in the collection to reassure the YSL faithful. But for the most part, he's high on classic shapes this season, in both skirts and pants.

As always, he gives his classics new dash. The tunic, the blouson, the pesant styles, even the shirt is back at Saint Laurent this season, touched with a ruffle. And his shifts have been rejuvenated with belts tied low on the hips to hike them to miniskirt length. He has added many silk print dresses that should be big sellers. His new classic jacket is shorter, with a rounded sleeve, and skirts fit flat over the hips thanks to a yoke. For evening, one can look Siamese, Chinese ort tailored in black tailleur.

Meanwhile, other designers are just catching up to Saint Laurent's old theme -- lots of different pants in all shapes and lengths. Karl Lagerfeld likes Bermuda shorts that button with a slit on one side, like a kilt. Valentino shows a lot of jodhpurs cut off at the knee, or toreadors. Kenzo goes strictly for short shorts or pedal-pushers, avoiding the Bermuda entirely.

Trends that won't take long to show up in Washington are:

Gold -- in a rush to make things look more special, lurex threads are shot through knits at Kenzo and elsewhere; in the YSL collection are cottons laced with gold, gold leather, gold piping and for good measure, gold accessories;

Blouson jackets and dropped waistline silhouettes lower the emphasis to the hips;

Mixed prints that seem to clash;

White -- showing up in every collection from daytime to evening -- and tan, which was pushed aside last season for all the brights.

Last year's exaggerated football shoulders are gone from just about every collection, and designers have used shaped sleeves to achieve a far more attractive look of width at the top.

Hemlines don't shock anyone either. How can one be upset about Bermuda shorts on the runway if the buyer sitting next to you is wearing shorts? And in the streets, the young Parisiennes are wearing sweaters that stop above the knee or long sweatshirts and thick tights, so on the runway they don't look very startling.

Hemlines for spring actually cut off everywhere on the leg, for both pants and skirts. Above the knee and below the calf seems to be the way it will go for the young trendies, while the more conservative will be content with hemlines around the knee. But if the Valentino customers are any example, women will be wearing shorts next summer.

If it all sounds a bit familiar, it is. Nothing takes any special explanation, nothing should challenge any customer. "I looked around at a meeting of store people," said Bloomingdale's Kal Ruttenstein, "and one buyer was wearing shorts, one knickers and one white leather jodhpurs, so it shouldn't be hard for the customers to understand them." The fact that many stores are already selling cropped pants such as Perry Ellis' culottes and Bermuda shorts and knickers is probably what has encouraged designers to produce all sorts of different pants, he added.

Stores are relieved that there are no dramatic changes this season. "Designers have finally realized that we are here to do business," says Ellin Saltman of Saks Fifth Avenue. "They've managed to stay sensible without being boring, and that's terrific."

Unlike other seasons, virtually all the clothes that made it down the runway were offered to buyers in the showrooms. Only Thierry Mugler made up a special collection just for the runway. "I knew sex was here to stay," said Saks-Jandel's president Ernest Marx after the Mugler show, "but I thought this belonged in the Crazy Horse Saloon, not on the runway." Yet when one Fifth Avenue store saw the collection made for sale in the showroom, it decided not to buy this season. Much too dull, was the conclusion.

"The priority for clothes is way down at the moment," admits Bloomingdale's Ruttenstein. "The list of things more important is very long. Still, women want to enjoy clothes and flaunt them. And for them this season has provided lots of fresh ideas."

"If it just gets us out of all the preppie clothes and into something else, that already makes it a good season," says Jane Vandermeade of Joseph Horne.