Exclusive: Katy Perry's Colorist: Why She Dyed Her Hair Blue After Split

Feelin' blue and lookin' blue, too?

Katy Perry may be licking the wounds from her failed 14-month marriage to Russell Brand -- he pulled the trigger with a Dec. 30 divorce filing -- but that has nothing to do with her latest hair color, which she debuted Thursday in Santa Barbara, Calif. during a shoot for an Adidas ad.

"Katy wanted to go this particular color blue for a few weeks now," the newly single singer's colorist Rita Hazan told Us Weekly in an exclusive chat.

The blonde shade that Perry, 26, showed off in December (with Brand, 36, at her side!) "was not an interim shade," Hazan points out. "She knew it wouldn't be permanent -- just another Katy Perry look!"

"It didn't take long to transition to this color as we have been working together previously," the celeb stylist adds. "We have a great relationship -- Katy is the ideal client because she loves to be creative and unpredictable with her look."

"She was great, really nice. She seemed happy," Perry fan Eric Berlanger said of Perry's demeanor on the Adidas set Thursday.

Adds a pal close to the "Firework" singer: "She is all about moving on now."