Health care folk like to have secret code words for things. It helps us feel special. And sometimes, it's really useful when we need to communicate without spooking the civilians.
A great example are hospital Emergency Alert Codes. If we need to call for assistance to deal with something unpleasant, like a fire in the building, we don't want to just yell "Fire in room 3102!" over the PA system. That's a good way to cause panic and get people hurt. Instead, we talk about it in code. Most hospitals nowadays are using color names for these-- though they can never agree on which color means what thing.
Apparently the whole thing started with Code Blue, which means a patient in cardiac arrest. It's named after the color you turn when you are getting no oxygen.
Once that rather morbid reference started to catch on, somebody decided it made sense to use Code Red to indicate a fire in the hospital. (It was an improvement over calling for "Doctor Firestone," which was supposed to hide even the existence of an emergency, but which wound up being harder to hear and not fooling anybody anyway.) From there the system has expanded so that nearly every conceivable emergency is labelled by a corresponding color.
At my hospital, Code Gray means a severe storm approaching. It's very cleverly assigned to the color of clouds, you see. We respond by moving the patients away from windows. If it worsens to an imminent tornado, they call Code Black, because black is like gray but more. Then we move the patients far away from windows.
Code Silver is also distinct from gray. It means an armed assailant in the building-- silver for the shiny metal gun. The protocol for this is amusing to read, where it explains complicated procedures like "leaving the area" or "going into a room and closing the door."
Code Pink means an infant missing from the nursery. As soon as
it's announced, quite a lot of personnel drop whatever we're doing and go
stake out all the entrances, exits, stairwells, and elevators in the
whole medical center. This has never actually been invoked for real, but we have
had surprise drills every so often, complete with a hired actor sneaking
through the building with a suspiciously large duffel bag.
After a certain point, the colors aren't as strongly associated with the event. Some emergencies are a bit too abstract to visualize so easily.
Code Green means security personnel are needed, stat. Note
that our guards don't wear or carry anything green, and they certainly
don't have green uniforms. I suppose the color is meant to invoke some military connotation.
Code White means evacuation. The best mnemonic I've come up with is to equate the empty building to a blank white sheet of paper.
Code Amber is theft or vandalism.
Code Yellow is a bomb threat.
There's a Code Orange, but unfortunately it's not just a Code Red and Code Yellow at the same time. Instead it indicates a hazardous chemical spill.
Code Purple is an "escalated patient event." Somebody has gotten violently loopy and requires immediate de-looping. This code summons the same security guys who would respond to Code Green, plus a crisis intervention nurse with a set of restraints.
I think my favorite is Code Violet. If this is ever announced, it means a sitting head of state has wound up in our emergency room after an assassination attempt. Seriously! There's a whole set of protocols that specify which of the entrances get locked down, which way we divert incoming ambulances, how many personnel can be coming in or going out at any one time, and lots of other stuff. It's written in such excruciating detail, I bet whoever specced it out is the type of person spends every weekend playing wargames and D&D. (In other words, they're a geek after my own heart.)
And of course, nurses talk about one that is not on the official list: Code Brown. This is completely informal and would never be announced over the PA. It refers to a much smaller kind of disaster-- the kind that necessitates changing a patient's gown and all their bed linens. Time to double glove, watch where you step, and remember not to breathe too deeply through your nose.