Today, Kelly is test-driving Pruitt’s forthcoming collaboration with J Brand for which the artist has lent the style and technique of his gradient canvases—certainly one of the artist’s trademarks, along with sparkly panda bears—to designer jeans. While most customers will buy their dégradé denim pre-painted from Barneys, who will exclusively sell the collection, Pruitt has agreed to personally airbrush Kelly’s pants while she is wearing them. (Barneys, in partnership with Leitzes & Co., who organized the collaboration, will also stage a similar site-specific spray booth at its Madison Avenue store on October 21.)

Rob Pruitt x J Brand jeans Photographed by Kathy Lo

Initially, we go in for a progression from aquamarine ankles to lavender waist. “That’s beautiful,” Pruitt says, admiring the work his assistant Kevin has started. “I like it on your shirt a little bit. And those boots, too,” he continues, referring to her now splattered oxblood Doc Martens. Someone suggests that Kelly’s shirt get the Pruitt treatment, too. “I’ve done weirder things,” Kelly says, gamely. Before long, Pruitt is blasting Kelly’s shirt up to and including her neck with a spray gun full of maroon pigment, “like at a tanning salon,” it is suggested. Passing thoughts of the paint’s toxicity are ignored—this is too much fun—and soon Kelly’s platinum tips are tinted the same amaranth color of her top. “You should dye your hair like that!” declares Pruitt, a longtime fan of denim as an artistic medium—he featured blue dungarees filled with hardened concrete in his fall 2006 show at Gavin Brown’s Enterprise.

Rob Pruitt x J Brand jeans Photographed by Kathy Lo

Just as we’re about to wrap, Kelly suggests that she paint Rob, in return. He goes for a dusty blue mixture before she uses the spray gun to give his once graphite-colored shirt a horizontal ring around his chest and back. “I love it!” Pruitt affirms. When we exit the studio and re-emerge into the early October haze, the feeling of fall is all over Kelly’s new clothes: They’ve gone from crisp summer whites to a mélange of richly moody autumnal color. The rest of the day, it rained.

Rob Pruitt x J Brand jeans Photographed by Kathy Lo

Rob Pruitt x J Brand Custom Bespoke Degrade Denim is available at select Barneys New York stores and on Barneys.com on October 15.

On Connor: Petit Bateau women's short-sleeved crew-neck tee, $23; petit-bateau.us; J Brand x Rob Pruitt custom bespoke degrede denim, $950; Barneys New York, NYC, 212.826.8900