Starbucks put new limits starting Monday on what its baristas can wear under their green aprons. The dress code requires employees at company-operated and licensed stores in the U.S. and Canada to wear a solid black shirt and khaki, black or blue denim bottoms.

Under the previous dress code, baristas could wear a broader range of dark colors and patterned shirts. Starbucks said the new rules would make its green aprons stand out and create a sense of familiarity for customers as it tries to establish a warmer, more welcoming feeling in its stores.