No one's suggesting that bank presidents will be prime customers for the more flamboyant outfits shown at the Paris fall menswear collections. But many of Los Angeles' corporate types are adopting an adventurous attitude. Brooks Bros., for example, has begun offering pleated pants--for their cutting-edge clients, of course. Beyond that, says Sean Townley of the L.A. store, men are asking for "color in striped braces; combinations such as red, blue and green. Or solid yellow braces, probably worn with a navy or gray suit." Leonard Durham, of Neiman-Marcus' men's furnishings shop, agrees: "Clients are dressing with a bit more flash these days--more colorful ties, or alligator shoes or belts." The anti-corporate contingent wears anything it pleases: perhaps Cerruti's acid green nylon pants, above left, Yohji Yamamoto's gray-and-red patterned jacket with polo shirt, above right (both at Maxfield), or Kenzo's iridescent cropped jacket and pants (at Neiman-Marcus).