honestly i would suggest not wearing any kind of shirt with a logo bigger than a fist. anything bigger than that looks unprofessional and not very brand. of course it also depends on what you do and how many guests you see. if you're overnight, it's whatever. I've seen overnight wear practically anything they wish as long as it follows procedures. if you're day time, I would suggest the color of the shirt match the color of the Target logo. Depending on your store though, you can usually wear any shade of red.
I wear a button up red shirt from Target or sometimes a red polo with a small little logo on the chest.