The greens were the faction of House Targaryen and their loyalists who supported the ascent of Aegon II as King of the Seven Kingdoms during the Dance of the Dragons. They were opposed by the blacks.
Their name derives from a great tournament held in 111 AC at King's Landing on the fifth anniversary of the King Viserys I's marriage to Queen Alicent Hightower, his second wife. At the opening feast, Queen Alicent wore a green gown, whilst Princess Rhaenyra Targaryen, Viserys’s daughter by his first wife, dressed dramatically in Targaryen red and black. Note was taken, and thereafter their respective factions at the royal court imitated the fashions they set - the "queen's party" dressing in green, and the "princess's party" dressing in black. In time, it became the custom to refer each party as simply "the greens" and "the blacks". 
Royal Targaryen Members
- King Aegon II Targaryen, King of the Andals, the Rhoynar and the First Men, Lord of the Seven Kingdoms, Protector of the Realm, rode Sunfyre.
- Queen Helaena Targaryen, rode Dreamfyre.
- Prince Aemond Targaryen, Prince Regent and Protector of the Realm, rode Vhagar.
- Prince Daeron Targaryen, rode Tessarion.
- Prince Jaehaerys Targaryen, bonded with Shrykos.
- Princess Jaehaera Targaryen, bonded with Morghul.
- Prince Maelor Targaryen, possessed a dragon egg.
Aegon II's Kingsguard
Defected to the greens
Other notable greens
Men from the Reach