I'm a barefoot G.R.I.T.S. but I've never done the one shoe off, one shoe on (I get a chuckle just thinking about the look on the postman's face!) However, my mother once went to work with one red shoe and one navy blue shoe on! When she retired they did a skit and it included 2 colors of shoe. I asked mom if she'd done the navy blue/black thing and she said not, it was not that subtle.