In her first official public appearance since parting ways with ex-husband Russell Brand, Katy Perry played host at the 1 Oak At The Mirage grand opening in Las Vegas. The newly-single star rocked a colorful blue coif as she was joined at the soiree by J. Molinari jewelry designers Markus Molinari and Jason Arasheben, as well as hotel heiress sisters Paris and Nicky Hilton, Shenae Grimes, Christina Milian and David Arquette. Perry looked sexy in short black dress with very stylish sandals.