"Green with envy" is one of several English sayings that have to do with the state of being jealous of the good fortune of another individual. Typically, this jealousy manifests as a desire to obtain possessions, friendships, jobs, or even love interests that are the same or similar to the person who is being envied. Being green with envy in the extreme does have the ability to seriously undermine confidence and may also damage relationships to the point that they cannot be healed.
There are several different proposed origins for the idiomatic expression green with envy, with one having to do with the Judeo-Christian tradition. One school of thought holds that the Hebrew word that most closely corresponds with envy is quinah, and has to do with changes that take place in the color of the complexion when a person is coveting the wealth or good fortune of another. Supposedly, this envy causes the body to manufacture greater quantities of green bile, which in turn affects the complexion.
A different origin for green with envy within the same tradition holds that the phrase is symbolic of the jealousy that Cain felt for his brother Abel, motivating Cain to murder his brother. The green connection is associated with the fact that Cain is identified in Jewish and Christian writings as being a farmer, who would in all likelihood have grown at least some green plants. Still other purported origins for this phrase point toward a slight adaptation of references to green-eyed monsters that are found in the works of Shakespeare.
Whatever the origin of the idiom, there is no doubt that green with envy is well-recognized as being jealous of and desiring to possess something of value that is in the possession of another person. It is possible to be green with envy when a coworker is promoted to job that you wanted for yourself, or a friend establishes a healthy love relationship while you are currently alone. It is even possible to be jealous of someone who seems to be happy with their lives, especially of the envious individual is not particularly happy with his or her own life at the present time. When carried to extremes, this type of envy can be the cause of breaking up long-standing relationships, lead to the loss of a job, and in general make the person suffering from the envy more unhappy than before.