You were dressed VERY similarly to the store's employees.
I disagree. Wearing an apron alone does not count as "dressed VERY similarly to the store's employees". As further evidence, I will point out the differences in the Publix and Cracker Barrel uniforms.
Publix uniform #1 - green polo shirt with black apron
Publix allowed uniforms (note not all of them even have aprons)
Cracker Barrel uniform - shift lead (blue Oxford shirt with red apron)
Cracker Barrel uniform - regular employee - this is what I was wearing
My particular location doesn't allow tan pants due to the manager's personal decision-making, but otherwise, as you can tell, the uniforms are very different. As I pointed out in the above post, most Publix employees also choose not to wear aprons (unless they work in the deli or sampling, where they're required to wear them). The woman at the check-out had a green vest on a white shirt.
This is simply a case of people not even bothering to take notice of the people around them.
Also, I can't help thinking that if Publix actually had more employees on the floor, then this wouldn't have happened, because the real Publix employees would be available to actually help the people asking me for help.