Col. Jeff Cooper's Color Codes for States of Awareness
White - Relaxed, unaware, and unprepared. If attacked in this state the only thing that may save you is the inadequacy and ineptitude of your attacker. When confronted by something nasty your reaction will probably be, "Oh my God! This can't be happening to me."
Yellow - Relaxed alertness. No specific threat situation. Your mindset is that "today could be the day I may have to defend myself." There is no specific threat but you are aware that the world is an unfriendly place and that you are prepared to do something if necessary. You use your eyes and ears, and your carriage says "I am alert." You don't have to be armed in this state but if you are armed you must be in yellow. When confronted by something nasty your reaction will probably be, "I thought this might happen some day." You can live in this state indefinitely.
Orange - Specific alert. Something not quite right has gotten your attention and you shift your primary focus to that thing. Something is "wrong" with a person or object. Something may happen. Your mindset is that "I may have to shoot that person." Your pistol is usually holstered in this state. You can maintain this state for several hours with ease, or a day or so with effort.
Red - Fight trigger. This is your mental trigger. "If that person does "x" I will shoot them." Your pistol may, but not necessarily, be in your hand.
States of Awareness, the Cooper Color Codes
By Tom Givens
Most people stumble through life, blissfully unaware of the world around them. They remain preoccupied with thoughts of work, or personal problems, or how to get a date, or other trivialities, with no thought to their immediate environment. By not paying attention to their surroundings, they place themselves in needless jeopardy.
Go sit in the intake area in your neighborhood hospital emergency room one evening, as an educational exercise. Observe the unfortunates who come in for treatment, and you will get an excellent illustration of this point. About twenty percent of the customers are actually sick-discount them. The remaining eighty percent are there because they were inattentive to their environment. These will be people who walked off loading docks, or stepped off ladders twenty feet up, or backed into running machinery, or stepped into the path of a vehicle, OR allowed a thug to walk right up to them un-noticed and bean them with a brick. You can be stupid, inattentive, and oblivious in your work environment day in and day out and get away with it until one day the odds catch up with you and you are injured. The same applies on the street. You can be stupid, inattentive, and oblivious and get away with it until your path happens to cross the path of a criminal. The vast majority of criminals are opportunists, who only strike when presented with a viable opportunity. Remove the opportunity and you remove the risk to you!
By learning to observe your environment, constantly evaluate it, and react appropriately to what you see, you can achieve a large degree of control over your fate. This requires you to learn to shift up and down a scale of readiness, just like shifting gears in a car, so that you can match your level of awareness/readiness with the current requirements of your situation. In a car, you shift gears based on the grade encountered or the speed desired. On the street, you must learn to "shift gears" mentally, to match the threat level encountered. There is a sliding scale of readiness, going from a state of being oblivious and unprepared to a condition of being ready to instantly do lethal violence if forced. One cannot live stuck at either end of this spectrum.
If you try to live at the bottom of the scale, you will fall victim to an accident or to a criminal, eventually. It's just a matter of "when", not "if". On the other hand, you can't go through your daily routine with your hand hovering over your holstered pistol, ready to shoot if anything moves! What you must learn to do is escalate and de-escalate up and down this scale as the circumstances around you dictate. This is an easily learned system, and one that will help you be in the right frame of mind to deal with any conflict you encounter.