From the Ultra Boost to its coveted collaborations with Kanye West, it seemed like adidas just couldn't lose in 2015. As successful as those projects were and continue to be, it was actually the retro Superstar shell-toe—with over 15 million pairs soldand its numerous releases with Pharrell Williams that really moved the needle for the brand.

In a new interview with Billboard, adidas Global Category Director of Statement Collaborations Rachel Muscat explained how the highlight of the Pharrell partnership, the 50-sneaker "Supercolor" collection, came to be. According to Muscat, adidas first linked up with Pharrell in January of 2014 and allowed him to browse the brand's archives. "He remembered how people had a huge connection to the Superstar from back in the day," Muscat said.

Just a few weeks later, the group was sitting down for lunch when Pharrell pitched the idea of making 50 colors of the Superstar. adidas then armed Pharrell with a Pantone color book, which the artist used to select the different colors for the collaboration.

"Three months later, with a suitcase full of shoes, we went to meet him backstage while he was on tour at his show in Dusseldorf, Germany," Muscat said. That's when they snapped the above photo of Pharrell sitting in the middle of the color wheel, which Muscat says was adidas' most tweeted image of 2015.

Muscat also hinted at what's next for the Pharrell partnership, adding that there's something new coming out in May. "I can’t tell you much more than that now, but we've been working on it with Pharrell for the last 6 to 12 months."

Read the full interview here.