Final answer:
Gawain wears the green scarf as a symbol of his guilt and shame for lying to the Green Knight in 'Sir Gawain and the Green Knight'.
Step-by-step explanation:
In the poem 'Sir Gawain and the Green Knight', Gawain wears the green scarf as a symbol of his own guilt and shame for not being completely honest with the Green Knight. After the Green Knight reveals that he is the same person Gawain met at the castle and testing Gawain's integrity, Gawain confesses that he kept the green girdle given to him by the lord of the castle, which he believed would protect him from harm. The green scarf serves as a visible reminder of Gawain's moral failing and his acceptance of his own human fallibility.