I found that in many hospitals, in order to classify patients' health conditions, standard expressions like "code red", "code blue" etc. are used. These expressions do not follow the standard "order of adjectives (adj+noun)" rule. Could you kindly explain this?
Compare filling in a form:
It is an abbreviated way of giving information What is the code for this patient's condition? It is red.
In speech you can't see the punctuation but this is what is understood by it.
Imagine you are a nurse reading from a form as the patient is wheeled down the corridor. You might read out:
Red is serving as a category or name, rather than as an adjective. The fact that it can be used as an adjective elsewhere is irrelevant. The different categories could have been called Paper/Rock/Scissors, in which case you would say Code: Paper / Code: Rock / Code: Scissors.
Well, they aren't quite standard, though different countries are moving to standardise more firmly so new staff will already be familiar with them.
It's to be remembered that they are all deliberately concise - so they can be used quickly - and deliberately opaque - it helps that many people won't panic if they hear a warning of a bomb threat, or that a child abductor might not know that "Code Adam" or "Code Kinder" mean the child's absence has been noted.
The format could be understood simply as e.g. "Code: Blue" or "Code: Atlas" or "Code: 100" etc, where the word is stated to be a code, and then the code in question given.
Even this though is a stretch, really they're best understood as codes, as one thing that stands for another thing, outside of the normal mechanism of language.
This applies all the more to the "Doctor" codes like "Paging Dr. Firestone to third floor ICU" meaning that there's a fire or suspected fire in the third floor ICU which should be evacuated as to the evacuation plan, but without alarming other patients and visitors.
I just noticed "in order to classify patients' health conditions".
There are two types of codes, and I'm not sure which you mean. Some are used as alerts, like E.g. "Code blue" often means "We have a cardiac arrest happening", but means other things in other hospitals, "Code Adam" actually started in supermarkets but is sometimes used in hospitals to mean a child is missing.
Then triage codes differ even more at different stages and in different places, then the number, colour, name or short description ("dead/immediate/urgent/delayed" for example) are simply given.