The first glance, the Green Knight is described to be impressive for his physical build.
"Half giant upon earth, I hold him to have been,
In every way of men the tallest he, I ween -"
Second to this physic, the next thing the author describes is his horse and attire; very green.
"All green bedight that knight, and green his garments fair"
"The very steed beneath the self same semblance ware,"
The author emphasizes the details and quality of the Green Knight's attire. (ex: They gleamed and glittered all with green stones rich and rare) Not only does this indicate that the Green Knight is of high importance, but his appearance hints that he may possibly be a mythical character.