Medical coding for medical records

In the hospital hiring manual, there is a series of "codes" which may be used on the loudspeaker (usually.) The codes are red, yellow, orange, green, blue, grey, silver, pink, purple, etc...

Code Yellow is very bad, since it means 'Bomb threat,' since evacuations are especially problematic in hospital.

Code Orange means toxic spill, Code red means fire, and there are specifics for whether to evacuate, or help rescue.

Code Grey means someone is brandishing a knife, and the usual protocol is for the staff to come this way, since a person with a knife looses confidence when surrounded.

Code Silver, however, means go away form this, since someone has a gun.

Code Pink means someone has kidnapped a baby. And Code purple I think is similar but an older kid.

Finally, Code Blue means a persons heart has stopped and needs life support measures.

Therefore, although I am only guessing, I think that when we hear the term "coding", it is a linguistic offshoot/ nickname of the original term "Code Blue."