It’s the week of cobalt dresses! Blake Lively kicked off the cobalt blue fashion show on Tuesday when she filmed Gossip Girl wearing a handkerchief style dress by Marc by Marc Jacobs (shop it at marcjacobs.com for $398). Catherine, Duchess of Cambridge followed two days later in a Stella McCartney shift, Lea Michele picked Oscar de la Renta on Friday, and Zooey Deschanel chose the hue when she wore Monique Lhuillier to last night’s Teen Choice Awards. “Fans of blue tend to be quiet and conservative,” Kate Smith, the expert behind sensationalcolor.com, told InStyle recently. “But those drawn to the brighter cobalt shades speak their minds when necessary.” Intriguing! When going with monochromatic cobalt, avoid frills in favor of clean, sleek lines, and pair the eye-catching shade with neutrals like nude, white, and black (notice Kate, Lea, and Zooey’s heels). For a more emphatic statement, combine cobalt with a bright opposite, like Blake did with her strappy coral heels.

Plus, see the silhouette the celebrities love right now!

Mermaid Dresses!

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