Dylan, Jealousy is complicated and so are the root causes. Jealousy is pretty complex, and can involve all sorts of emotions, like fear, anger and humiliation. There are many explanations for seeing green, and for decades, psychologists have been researching what may be to blame.
Jealousy is very emotional and, at times, difficult to work through. Acknowledge your feelings, talk with the person involved and shift your mindset to the positive parts of your life. These steps can help you break free from envious thoughts. You may want to seek help with a counselor to sort out what is triggering your jealous feelings.