When a person is referred to as a green person, it means that he or she is new to a certain position, work, hobby or activity. The term green is a metaphor for an inexperienced person for a certain field of endeavor. It is similar to a plant that just sprouted its fresh, green leaves in a certain location surrounded by other plants. Same with people who just had their first taste of real life experiences.
The term green people is often attributed to first timer workers or even officers who handled jobs in a new setting for the first time. For instance, a nurse who was recently been hired and is having a difficulty in adjusting to her new life is referred to as green. Another example is that of a police who handles his or first rescue operation but was not able to handle the situation well, is also said to be green. When the person is referred as green, it means that he or she is new to the job and mistakes can occur in the performance of his or her job. But being labeled as green also implies certain expectations. When a person made mistakes in his or her first job experience, the supervisors of that newly-hired person expects that such mistakes will not be repeated. Finally, the term green can also refer to a person who just transferred to another work setting. Even if he or she is well-acquainted with his job in the new workplace, he or she is still called a green person considering the fact that he or she is new to the workplace.