Katy Perry switched up her hair for the Met Gala after party to a yellow wig - dramatic! This image appears in the gallery:This Week's MUST-SEE Pictures From The World Of Music 45. Katy Perry switched up her hair for the Met Gala after party to a yellow wig - dramatic! Katy partied with her ex, John Mayer, at the after party. Picture: Splash 65 images See the full gallery: This Week's MUST-SEE Pictures From The World Of Music