A protest by Starbucks employees over the company's updated dress rules got bigger on Thursday.

Starbucks Workers United, a union for the company's U.S. employees, reports that over 2,000 baristas in 120 American stores have been striking since Sunday, disagreeing with the recently introduced dress code.

From Monday, Starbucks is introducing new rules about what its baristas can wear beneath their green aprons. The updated dress code applies to staff in company-owned and licensed stores in the US and Canada, requiring them to wear a plain black shirt and trousers or jeans in khaki, black, or blue denim.

Previously, baristas had more freedom to wear various dark colours and patterned shirts. Starbucks stated that the updated rules aim to highlight their green aprons and create a consistent look for customers, as they try to foster a friendlier atmosphere in their stores.

However, Starbucks Workers United, the union for employees at 570 out of Starbucks' 10,000 American stores, believes the dress code should be discussed as part of their collective agreement.

Paige Summers, a Starbucks supervisor, believes the company has lost sight of its priorities. She argues that instead of valuing its baristas, who are key to the Starbucks experience, the company focuses on less important issues, such as a strict new dress code. Summers added that customers are likely more concerned with long wait times for their orders than with the colour of employees' clothing.

Summers and others also criticised the company for selling Starbucks-branded clothes on an internal website that employees were no longer allowed to wear at work. Starbucks stated that they would provide each employee with two free black T-shirts when they announced the new dress code.

On Wednesday, the Starbucks Workers Union announced that 1,000 employees had walked out in 75 stores across the US. Starbucks stated that the strike action had a minor effect on its 10,000 company-run stores in the US, and in some instances, stores were closed for under an hour.

Starbucks stated it would be better if the union focused on returning to negotiations instead of protesting by wearing black shirts. The company added that over 99% of their stores are currently open and serving customers, as they have been all week.

Readers of the Associated Press expressed varied opinions on the dress code, with some arguing that Starbucks' baristas' complaints were unwarranted, as many retailers have similar requirements. Others felt Starbucks should prioritize beverage quality and prices, and employee satisfaction, rather than focusing on dress codes.

Maddie Mucklow, a Starbucks store manager in Seattle, has expressed her support for the new regulations.

Mucklow admitted the new dress code was a challenge for staff initially. However, she believes it provides a clearer framework for professional appearance, allowing for personal expression within certain limits.

Since 2021, Starbucks employees, organised as Starbucks Workers United, have been creating unions in stores across the U.S. Despite agreeing to resume negotiations in February 2024, Starbucks and the union haven't yet reached a final contract agreement.

This week, the union announced they had complained to the National Labor Relations Board, claiming Starbucks was not negotiating the new dress code.