Once upon a time, when The Smurfs in 3D was making its premiere rounds, singer-actress Katy Perry took the red-carpet interpretation of her movie character, Smurfette, very seriously. She dyed her hair blonde and she wore a short, frilly white dress with a bedazzled portrait of the heavily lidded cartoon. For the sequel, she toned down her Smurf enthusiasm and instead opted to simply nod (heavily) to the color blue. Yesterday in Cancun, she wore a lacy, three-quarter-sleeved Yves Klein blue Monique Lhuillier frock to a photo-call for The Smurfs 2 at the 5th Annual Summer of Sony held at the Ritz Carlton. She added silver pumps, blue-and-white sunnies, and a garland of royal-blue flowers in her dark hair. Our take? The Smurfs would coo in approval.