Julia Stiles has brains as well as beauty. When asked a question by a Colombian reporter at Ghetto Film School’s benefit at the Standard Biergarten on Wednesday, the “Bourne” star answered in fluent Spanish. Stiles explained she just spent two months filming “Out of the Dark” in Colombia. “I am trying not to lose the Spanish I picked up,” she told us. “I studied it in school and traveled a lot . . . I watch a lot of Spanish TV. My favorite show is ‘Caso Cerrado,’ which is the Spanish ‘Judge Judy.’ ”