More on the meanings of Green in Gawain and the Green Knight

When beginning our discussion of Gawain and the Green Knight, we made a list of different things that green could mean: envy, riches, nature, the muslim faith, etc. I think that you could fairly easily argue for many of these as being meanings behind the author's use of green. But I wanted to concentrate on the idea of green being symbolic of the muslim faith. Throughout the entire story, Sir Bertilak's court is obviously better than King Arthur. They are more sophisticated and treat their guests with extreme generosity- they even go to mass every day which makes them almost more "holy". So why is the Green Knight, the owner/ruler/liver/whatever of this fine and Christian court actually green, when one of the most obvious meanings to the people of that time period was the religion of their enemies? I first saw it as Gawain's faith being tested- which it is. He has to play the game that Bertilak has set up for him and prove the honor of King Arthur's court. However he doesn't fully pass. He gains his life, but he is carrying his shame from this experience for the rest of his life. The Green Knight actually wins in the end which, if following the muslim reading of green, means that Christianity loses. Why would the author do this? The way I saw it was as a message to the audience to keep the faith and to not end up shamed like Gawain. There could also be more lost in translation of the piece. I am hoping for the latter, for I am not satisfied with any of the answers I have come up with.