That is right, when the zombies gather to rip your brains out, you will be glad you have a cool paradigm on your side. So lets start with Jeff Cooper, famous for creating the modern technique of handgun fighting. Cooper served in the United States Marine Corp during World War Two and Korea. He came up with a colour code for the different states of awareness a person can experience. It is a combo of your psychological and physiological states.
You need to be in condition Yellow, where you are constantly observing your surroundings and alert for potential threat. When there is a possible threat, you switch into condition Orange, where you start to evaluate the threat and consider your plan of action. Maybe you are lucky and can avoid the threat but if you need to get physical then you switch into condition Red. That is the fight mode.
Now Cooper's code code only went to Red but the United States Marine Corp modified his code by adding condition Black. This is where your physiological state goes extreme and you essentially panic. So while Yellow to Red are all appropriate conditions to be in, depending the situation, it is the White and Black you want to avoid.
Bite off more than you can chew