If the military parade, stirred up by Italian fashion designers six months ago, passed you by, it doesn't mean you are out of step with the season to come.

Designers in Milan, presenting their spring collections as the first lap in a three-part marathon that will take buyers to Paris and London as well, have disarmed the military into a far more feminine look for spring. Buyers are seeing a mishmash of themes ranging from geisha girls to tropical princesses.

A new messages are coming through loud and clear, however. The military look is gone, except for some hint of khaki, a warm weather perennial. Shoulders are broad: waistlines are usually nipped in with a belt: skirts are narrow with slits; and pants start very full at the hips and fit tight at the ankles.

The new clothes generally stay close to the body, as at Gianni Versace where the narrow look is underscored, by midriffs wrapped in an oriental manner.

Paper-thin leather and suede, which began to show up in black for the fall, is also being used by many Milanese designers in white, beige and some bright colors. Krizia showed a leather bra under one outfit (there was also a gold bra); but for the most part, leather is substituted for silk or cotton in jackets, pants or skirts. Sometimes the leather is punched with holes, adding to the lightweight quality.

Giorgio Armani, for example, was showing a sexy mauve suede side-button skirt with a one-button jacket, and a Prussian-blue suede jacket with olive-green suede pegged pants.

There is a lot of leather, too, being worn on the streets in Milan. Yesterday New York model Yasmine was seen in Gianni Versace's brown pleated-leather jacket and suede pants, and her companion was ll in black leather.

Even more popular are the Glorgio Armani brown unlined jackets or blouses being worn by the buyers. According to one report, nine out of 10 of the buyers are wearing some piece of Armani clothing, and the 10th is in Calvin Klein.

Prints, which haven't been popular since a huge saturation several seasons back, are beginning to surface again. Polka dots are a favorite. At Basile they look like scattered powder puffs: at Krizia they line up evenly in black and white on chintz.

Val Cook of Saks-Jandel, who says she has yet to find one collection that is really a standout in Milan, is disappointed not to find a strong theme for the shows. And she admits that her customers will find two colors popular with designers there - a bougainvillea purple and garish blue-green - hard to wear.

"And finally, when the dsigners don't know what to do, they put a cascade of ruffles, a palm tree and on orchid someplace in sight, and that's not much of a winner either," complains Cook.

Some buyers are facing other kinds of taste problems. Kal Ruttenstein of Bloomingdale's is gearing up for the new slimmer look . . . his own. He's been passing up the pasta at most restaurants and traveling with his own supply of protein bread in a plastic bag. He's on the Scarsdale diet.