Green was a Vigo within the Black Sun organization, specifically under the command of Prince Xizor; he was a Human.
Due to his extensive network of informants, Green was hand-picked by the Falleen prince to serve as a Vigo. Xizor was aware of Green's aspirations to usurp the Underlord, but Xizor did not see him as a real threat. Many of Green's agents were, in reality, double agents working for Durga the Hutt. Xizor considered few of Green's schemes to be adequately profitable.
Following the Battle of Yavin, a former employee of Vigo Green retired to the planet Corellia, where he purchased land to breed large animals. Because this ex-employee still owed Green money and failed to adhere to the agreed-upon payment schedule, the Vigo hired a group of discreet hitmen to teach him a lesson. Consequently, the spacers went to the property and killed any creatures they could locate.
Eventually, Xizor learned that Green was secretly gathering intelligence on Black Sun for an unidentified external group. Consequently, Xizor ordered Guri to kill Green in front of the other Vigos as a demonstration. His position was then filled by another Human who, unbeknownst to the council, was actually Xizor's niece Savan in disguise.
During the Galactic Civil War, Green was a middle-aged man with a receding hairline. Green's extravagant attire was a reflection of his belief that such clothing earned him the respect of those who worked under him.