Thus, it’s hard to figure how the fashion trend of “naked dressing,” lamentable even at nightclubs, has invaded the precincts of ancient social custom. The traditional bridal dress is white for its association with purity, innocence and, yes, virginity. At Studio 54, the late ’70s disco of wild abandon, there actually was a dress code — though it took up only one line. Yet he was taken aback last week when, walking down a big city street in broad daylight, he passed a young woman who had wholeheartedly embraced the naked dressing aesthetic. Pronovias, the Barcelona-based bridal fashion house, ginned up quite a bit of press when it introduced naked dressing for brides.