ONTD's Fav Queen Natalie Goes Blonde

At the Van Cleef & Arpels Dinner for L.A. Dance Project in Los Angeles Saturday night, brunette beauty Natalie Portman -- clad in a white Dior Couture gown and Van Cleef & Arpels jewels -- debuted much lighter locks as she posed on the red carpet alongside Robert Pattinson. (Portman's hubby, choreographer Benjamin Millepied, was also in attendance.)

Both stars were in high spirits during an intermission, when the Oscar winner, 31, Pattinson, 26, and an unidentified pal chatted with Millepied. "They were very friendly," an eyewitness tells Us Weekly of Portman and Pattinson's interactions. "They were laughing aloud and smiling. Rob . . . was having a great time."

Pattinson -- who, as multiple sources have confirmed to Us, recently decided to take girlfriend Kristen Stewart back following her mid-July cheating scandal -- did his fair share of mingling, and even posed for a photo with a fan.

"At one point he was laughing so hard, he almost spit out his beer!" the witness says of the Twilight star. "He seemed to be enjoying himself."

As for Portman's dramatically different 'do? The mom to Aleph told fellow event-goers it's for a new role.

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