Gabourey Sidibe, Mariah Carey, Maggie Gyllenhaal and Mo'Nique sing the blues. Photos: Getty Images (4)

"Avatar"'s blue people seem to have had quite an influence on the red carpet -- among the gowns, that is, not just on Ben Stiller's Na'vi-inspired onstage getup.

And appropriately enough, the two stars of "Precious: Based on the Novel 'Push' by Sapphire" both wore sapphire-hued dresses. Gabourey Sidibe, nominated in the best actress category, wore what she called a "money shot" gown by Marchesa.

Sprays of hand-embroidered crystals embellished the neckline and waist of her silk chiffon, off-the-shoulder dress. Lorraine Schwartz decked her in blackened platinum-and-diamond bracelets, earrings and a ring.

Oscar winner Mo'Nique paid tribute to Hattie McDaniel with her royal blue gown and white flowers in her hair. McDaniel, the first African-American to win an Academy Award, had worn the same color and flowers when accepting her statue in 1940. Mo'Nique explained, "for you, Miss Hattie McDaniel, it's about time the world feels you all over them."

Maggie Gyllenhaal, best supporting actress nominee for "Crazy Heart," went out on a limb with a boldly patterned Dries Van Noten strapless column dress. This last-minute choice had a splashy deep blue, black and white handpainted floral pattern. Her ivory-colored drop earrings were shaped like angel's trumpet flowers.

Mariah Carey's navy Valentino gown, meanwhile, showed a lot of leg. The softly draped skirt was held at the waist by a whopping, sparkling floral brooch. She accessorized with H. Stern's Top Floral white gold-and-diamond bracelets and a pair of leg-lengthening nude platform heels by Christian Louboutin.

Oprah also chose navy for her moment onstage as a presenter, albeit with a lot more coverage.

One actor also had the blue blazes -- Robert Downey, Jr. wore blue-tinted sunglasses and an oversized blue bowtie!

Check out more Oscars 2010 trends and our StyleList best and worst dresses.