the Green is one of the four titles which can be unlocked by taking the Rune Guardian's test during the quest, Rune Mysteries. Depending on the player's test answers, they will receive either the Blue, the Green, the Grey, or the Red. After the quest, the player can return to the Rune Guardian and change freely between the four titles without retaking the test. Only one colour title may be unlocked at a time in the player's title interface.
This title changes according to the language of the server on which RuneScape is played, as shown below: