from the project “medium white shirt”:

From January 11 until February 9, 2017, writer and artist Emily Spivack, along with the Honolulu Museum of Art, opened a tee-shirt shack in Hawaii which sold only medium white tee shirts. It was President Obama’s idea.

According to an article in The New York Times from July 2, 2016:

Mr. Emanuel, who is now the mayor of Chicago but remains close to the president, said he and Mr. Obama once imagined moving to Hawaii to open a T-shirt shack that sold only one size (medium) and one color (white). Their dream was that they would no longer have to make decisions.