Starbucks’ new red cups are here for the holidays. Kristy Cameron, creative director for Starbucks, says the chain is "excited to lean into greens this year."

It is Red Cup Day at coffee giant Starbucks, an unofficial holiday for java fans who enjoy discounts and rewards. Here's how it works: Stop by a participating Starbucks store on Thursday and get a free, 16-ounce holiday-themed reusable red cup when you purchase one of the coffee chain's special seasonal drinks.

"Red Cup Day," a favorite Starbucks holiday tradition that offers customers free reusable cups, takes place this week -- but there's a catch.