In Arthurian legend, what colour was the knight pursued by Sir Gawain?

'Sir Gawain and the Green Knight' is a late 14th-century Middle English chivalric romance. It is one of the best known Arthurian stories, with its plot combining two types of folk motifs, the beheading game and the exchange of winnings. Written in stanzas of alliterative verse, each of which ends in a rhyming bob and wheel, it draws on Welsh, Irish and English stories, as well as the French chivalric tradition. It is an important example of a chivalric romance, which typically involves a hero who goes on a quest which tests his prowess. It remains popular in modern English renderings from J. R. R. Tolkien, Simon Armitage and others, as well as through film and stage adaptations.

It describes how Sir Gawain, a knight of King Arthur's Round Table, accepts a challenge from a mysterious "Green Knight" who dares any knight to strike him with his axe if he will take a return blow in a year and a day. Gawain accepts and beheads him with his blow, at which the Green Knight stands up, picks up his head and reminds Gawain of the appointed time. In his struggles to keep his bargain, Gawain demonstrates chivalry and loyalty until his honour is called into question by a test involving Lady Bertilak, the lady of the Green Knight's castle.