But by drifting away from the smock and the vest — long emblems of the working class — Wal-Mart is also leaving behind a uniform that linked it, at least in the popular imagination, to its largest customer base.

“This is much more business casual” than working class, said Mr. Herman, who in the 1980’s introduced shorts to the uniform of Federal Express employees and the first cotton shirt at McDonald’s, which had long been wedded to 100 percent polyester tops.

Consumer companies have always viewed their employees as an extension of their brand name, and have dressed them accordingly. Employees at Southwest Airlines, for example, wear a polo shirt and sneakers to convey the company’s no-frills, discount culture. The salespeople at the teenage clothing chain Abercrombie & Fitch wear baggy pants and tight-fitting shirts to project the image of sex appeal and youth.

Taraynn Lloyd, director of marketing at Edwards Garment, a major uniform supplier in Michigan, suggested that Wal-Mart might be arriving a bit late to the polo party. Many companies that require uniforms are now moving away from polo shirts “toward a more tailored look” — namely, button-down, woven shirts.

Outfitting more than one million workers with new clothes could prove costly for the penny-pinching Wal-Mart. The retailer said it would supply each employee with two navy blue polo shirts (employees can substitute a dark blue dress shirt). The chain may eventually cover the cost of the khakis, too, but for now, workers must buy the pants, which retail for about $15 at Wal-Mart, on their own.

Some workers are not eager to dig into their own pockets to pay for the khaki pants. Aubretia Edick, who works at a Wal-Mart in Hudson, N.Y., said in an interview that the dress code was “very crisp” but questioned why she should have to buy her own pants if she does not normally wear khakis. “I am buying these pants for work, and that is it,” Ms. Edick said. She was referred by WakeUpWalMart.com, a union-backed group in touch with the company’s employees.

Wal-Mart began testing the clean-cut polo and khaki outfit a year ago at a handful of stores and has since introduced the look at every store the chain has opened since early September.