Margot Robbie dazzled at her inaugural Met Gala on Monday night. The Aussie actress wore a Prada  custom-designed powder blue silk organza tea-length dress, with her hair pulled back for a decidedly sophisticated look. The actress turned heads at the Metropolitan Museum of Art's Anna Wintour Costume Center, just as she did throughout award season, though her newly dark-brown 'do  is a stark change from the blond locks she's most recognized for. This year's Met Gala celebrates American-based designer Charles James . He was best known in the '40s and '50s for glamorous ball gowns that highlighted a woman's curves.