THERE'S ALWAYS BEEN a standoff between men who wear boxer shorts and those who wear Jockeys. Tighter, more body-revealing underwear was standard until the early 1900s when, according to Richard Martin and Harold Koda in "Jocks and Nerds," boxer great Jack Johnson was forced to switch to boxers because his physique in skin-tight shorts intimidated his opponents. Today's bold patterns, bright colors and handsome haberdashery prints in combed cottons and silks remain unseen, of course, under business suits and other work-week garb, but lately they have been turning into outerwear. They peek out from under gym shorts or are worn over tight spandex shorts a la Agassi. And yes, women wear them, too.