Condition green was a pre-arranged code phrase used by landing parties of the USS Enterprise when communicating under duress. Declaring the party's status compromised, but not in immediate peril, it instructed the ranking officer aboard ship to take no action. It did not prevent that officer from preparing for possible future actions. Nor did it prevent that officer from using considered judgment to exploit an opportunity that aided the party without violating mission parameters. (TOS: "Bread and Circuses")

This, and other known code phrases like chess problem were applicable only under certain circumstances and rarely used. Presumably, such codes were part of a "play book" devised by Captain Kirk and his officers ^{(citation needed • edit)} to cover a wide range of scenarios. (TOS: "Whom Gods Destroy")