I'm pretty sure it's a bug. It happens to me also with the colossal scimitars I have. It seems to be only from one side it appears like that, then on the other side it looks like normal in a lot of areas. I've also noticed that it seems to turn the color of whatever the base background color behind all the textures and skins and such of the area is, or whatever you want to call it.
I'd most definitely call it a bug and not intentional. It's pretty annoying, too.