I disagree with Cooper on several points, one being his requirement for yellow.
Where Cooper was or was not right could be a thread that would lead to lots
of arm waving and incoherent screaming.
Pax's nap is an excellent example of the absurdity of the requirement.
As a confirmed coward, I read Cooper's "Principles Of Self Defense" with some amusement. Having been a victim of crime, and having submitted to force (while armed, no less) I do not appear to meet Cooper's definition of a man. Fortunately, that is not the definition that matters.
I'm thinking of forming an association along the lines of "Armed Cowards".
The reason this bears on the color codes is that a coward's "red" trigger is probably lower than that of a brave person's trigger.
We scare easier.
Another reason I don't teach the color codes is because it's very similar to pain-- it's too personal to lay out uniformly. The pain that is an 8 to some people is a 3 to others, and the alert state of mind that would be red to some people would be asleep to others. The scientist who performed experiments in London and who were "mildly annoyed" by the blitz come to mind.
I teach two states to my self defense students, with a hair line in between: before the break in concealment and after one opens fire.
I teach avoidance and de-escalation. I teach cowardice, I teach leaving, running if you're followed, begging if you're caught.
If none of that works, and when the alternative is worse than a life in prison, then I teach two ways to open fire.
There is no color in any of it, but then I'm not very tactical.
The best reason I don't teach color codes is that there is no pre-arranged system, there is not a specific trigger, action, state of mind, event or anything else that can tell you when to draw and open fire.
Every situation is unique.
While it can be argued that practicing a higher state of alertness may prevent
the need for a weapon, it can also be argued that that is independent of the weapon, and can be practiced without a weapon.
Therefore, tying a color code to weapons training strikes me as a mixed message, because being alert is a Good Thing (tm) with or without a weapon.