In the fashionable French trench, tacky khaki is out and polyester is in.

The berets can stay but unpleated pants got their marching orders as the army paraded its new uniforms at an unusual fashion show.Not everyone was wild about the styles; some full-figured soldiers complain they may have to wear girdles to squeeze into the new skirt-pants for women.

The parade showed blousons for all enlisted persons and straight, pleated pants for men and women. The lighter fabrics and colors with contemporary style and practicality make army gear look made more for fashion than fighting.

"It was time for a change," said Gen. Gilbert Forray, chief of staff of the army, who helped engineer the creation of the uniforms, which had not changed for 40 years. The uniforms were ordered from the house of Balmain.

Balmain, which also recently redesigned uniforms for the French police, was chosen after polls conducted within the army to determine which cuts, colors and fabrics would best suit the needs of today's army.

The clothes were designed by Balmain's couture designer Erik Mortensen and Patrick Aubert, head of the company's masculine fashion department.

The fashion parade, after opening with some flamboyant red-white-blue braid-edged redingotes from the time of Louis XV, displayed what the new officers, gentlemen and women will wear in the service beginning in 1991.

The new blousons with a shoulder-to-waist pleat are both sober and chic. The clothes are topped with kepis for officers or sharp berets with wheel-shaped pins.

"And thank heaven they didn't get rid of the kepi," said one male fashion observer, who noticed that male officers would still sport the hat silhouette as distinctive as Charles de Gaulle's.

Khaki is out in the new military palette, a lighter shade of putty or pewter called "terre de France" is in, and in a lighter fabric - a mix of wool and polyester, rather than heavy twill.

"It's more practical, a lot less gear is involved now, and it's more elegant," said Capt. Denis Brunel.