They are citing independent sources saying that Reynolds is utilizing "a grey tracking motion/performance capture suit with led lights" to make this happen.
http://www.slashfilm.com/2010/04/11/exclusive-green-lanterns-suit-will-be-almost-entirely-cg//Film goes on to cite the films costume designer Ngila Dickson (Academy Award winner for The Lord Of The Rings: The Return of The King) as being solid proof that this should work.
Ngila was tasked with trying to find a way to do something that stands apart from all of the other superheroes spandex suit designs we've seen in the past.
They also went on to say that the medium of CG is actually quite suited to the look of the Green Lantern's costume:
The Green Lantern suit is something that should look alien - it needs to seem other worldly. It encompasses any creature that wears the ring, and Hal Jordan is the first human to ever wear the suit. This was a chance for Dickson to do something different. You also have to consider that Hal changes into the suit multiple times in mid scene, and the cg also allows him to do this.
Lastly, it seems that the look of the the suit will keep in line with the actual story being told in the film:
I've heard that when the cg is complete, the suit will look like a manifestation of his power.