If you noticed that some of your Jewish coworkers were wearing out of the ordinary shoes today, like, for instance, Chuck Taylors under their suit pants, it's not because they were trying to "kick it out school." You may think that's why, but it's not, so don't say that.
In general, if you ever notice that a Jewish coworker is wearing anything out of the ordinary, just assume it's for religious purposes. That's always the safest route to take, much safer than cracking jokes in the elevator.
I have a migraine. If I didn't have a migraine, this post wouldn't be so lu-hame.