Harmy said:

Oh, yeah sure, I see.

Haha, alright. Not sure if you're not taking me seriously just because I'm referencing a prequel.

But there's actually a really great example of this in Return of the Jedi, too.
http://img805.imageshack.us/img805/9413/saber2.png

Notice the same glow of Luke's saber around the edges of the walkway (though it's a little bit too much, given the saber's brightness). The walkway doesn't cast a colorless mask around the saber, like it does for Vader's saber (which looks wrong for a light source)