I am familiar with the Colonel's color code system. From a real world perspective, I don't do white anymore. Yellow is when I am in my office or my house, where I know there is a hard barrier between me and the outside and risk of confrontation is as low as possible (I sleep so lightly now, white is practically unachievable).

Orange is when I am in general public and under uncontrolled conditions, such as the commute to work, or shopping, or eating at a restaurant. Red is when I am out hunting, or detecting an alarm or distress in my vicinity.

Black occurs sometimes if I hear a noise that reminds me of a mortar attack, or if I get confronted abruptly while not in the red zone. It doesn't last, but it catches me unaware, and I have to stop and think about my situation before I can decide what to do. It is paralyzing. I have yet to experience a direct red to black transition, though I suspect such an event is possible. One example might be to expect a confrontation from a few and end up abruptly facing hordes while woefully underequipped for such a melee.