The singer rocked the red carpet in a show-stopping Alexandre Vauthier gown with a 20ft feather train.
Her dress was so long that Rita's stylist had to accompany her as she posed for photographers, walking behind her to lay out her gown as she sashayed down the red carpet.
CLICK ON PHOTOS FOR FULL GALLERY
A sparkling bodice with a plounging neckline was separated from the baby blue-coloured feather train by a black and silver sash around the waist.
Five inch, black and gold stiletto heels with ankle straps completed the star's breathtaking look, along with a chin-length blonde bob and natural make-up.
Taylor Swift and Selena Gomez also opted for blue for the musical night out in the Big Apple, taking it down a few shades to a deep navy blue.
But the colour was the only thing Selena, 21, toned down. The former Disney star wore a daring Atelier Versace embellished floor-length dress complete with cut out bustier.
The daring gown was held together with silver clasps, the hooks left open to reveal a risqué sheer black bustier beneath.
Taylor Swift, meanwhile, channelled her Hollywood screen siren look in a plunging, body skimming Hervé Leger number.
Lorraine Schwartz jewels added another touch of glamour to her red carpet outfit. The 23-year-old country singer went even more vintage by wearing her usually poker straight blonde locks curled into a Twenties hairstyle. Her signature red pout added to the classic theme.