[Frodo Baggins]

Green Knight aside, the color green as an evil color was a rare thing to the medievals. To them, green was susally the colour of hope and new things. It's all over Dante. In the Valley of Princes on the mount of Purgatory two angels arrayed in green (hope) descent to defend those in the valley from a great serpent that comes. And also in earthly paradase atop purgatory dance the three theological virtues, Faith, Hope, and Charity. Hope is a green lady arrayed all in green.

It hink it is, however true that any color can be representative of good or bad. Green leaves, green moss, green grass are good things, green stuff that grows on decaying things is nasty and smells. Take another colour, red. Red is the color of love and passion, perhaps even royalty (though that's usually reserved for blue and purple) but red flags have often been a symbol of no mercy. When an army raises a red flag, it dosen't mean they love thier enemies it means (usually) "We take no prisoners".

Oh, by the way, the scarf the lady gives Sir Gawain to protect him from wounds is also green.