Starbucks workers at four stores across Colorado went on a strike on Thursday, joining employees at more than 100 nationwide stores, Starbucks Workers United said.

Workers in Colorado are striking at the following locations:

• Garden of the Gods at 4465 Centennial Boulevard, Colorado Springs, from 5:30 a.m. to 7 p.m.

• 3rd and Columbine at 250 Columbine Street, Denver, from 5 a.m. to 7:30 p.m.

• Rock Creek Circle at 2800 Rock Creek Circle, Superior, from 6 a.m. to 2 p.m.

• 11th Avenue at 2604 11th Avenue, Greeley, from 5 a.m. to 9 p.m.

The strike, which workers called the “Red Cup Rebellion,” demands that Starbucks fully staff all union stores and “begin bargaining in good faith.”

The strike takes place on the corporation’s Red Cup Day, when Starbucks offers free branded cups with select purchases.

“Each year, our partners and our customers look forward to Red Cup Day as an opportunity to celebrate the holiday season while creating moments of joy with one another over handcrafted coffee,” a Starbucks spokesperson said.

The union said demonstrators will strike outside of stores and hand out Starbucks Workers United branded cups to customers instead.

“Starbucks partners are the face and foundation of the company, yet they are forced to run perpetually understaffed stores while working inconsistent schedules they cannot rely on,” the union said in a press release. “Conditions like these are what led Starbucks partners nationwide to begin unionizing, and the company has only responded with disdain and disregard for its employees.”

A Starbucks spokesperson said the company is aware of the demonstrations and respect the workers’ right to engage in lawful protest.

“We remain committed to all partners and will continue to work together, side-by-side, to make Starbucks a company that works for everyone,” a Starbucks spokesperson said. “In those stores where partners have elected union-representation, we have been willing and continue to urge the union to meet us at the bargaining table to move the process forward in good faith.”

Starbucks workers at the 2400 Baseline Road location in Boulder also announced their intent to join Starbucks Workers United early Thursday. This is the first time Boulder Starbucks workers have asked Colorado’s labor board for a union vote.

If the Boulder location also wins the election, it will be the ninth in Colorado to join the union.

In a letter to management, Boulder workers said they want to unionize to “actualize the values Starbucks claims to hold.”

“Despite the countless conversations and meeting we have had with our management over the course of many months about providing our partners a livable wage, we have made no progress,” organizers wrote in the letter. “After facing an unresponsive management, we are left to partner with Starbucks Workers United to amplify our unheard voice.”

Workers claimed that company prices are climbing, staffing is reduced and baristas are paid 30% below livable wage.