Something I’ve never quite understood: if in the classic version of the Green Lantern Corp their rings don’t work against anything yellow, then why aren’t they all utterly and completely helpless against Sinestro’s yellow power ring?
AIUI, the GLs dealt with fighting Sinestro by dodging his yellow energy blasts, using their rings to drop things on him, create environmental effects, etc., as going head-on against him didn’t directly work.
I think it was in one of the old Super Friends cartoons where Sinestro trapped Green Lantern in a cage of yellow energy and banished him to deep space. Green Lantern escaped by somehow causing the cage to spin faster and faster until the color changed from yellow into something that he could affect with his ring. It seemed like a pretty genius move to me.
AFAIK, at some point Parallax was removed from the big lantern battery on OA and that removed the weakness against yellow from all green lanterns.
It looks like this happened in 2004-2005, in the Green Lantern: Rebirth miniseries; the fact that Parallax (the embodiment of fear) was imprisoned in the power battery was revealed in that series, and served as a retcon explanation as to why GL rings had the “yellow impurity.”
AIUI, the absolute weakness against the color yellow was significantly reduced, but not entirely eliminated: a GL with sufficient willpower and experience can now overcome the yellow problem, but less-skilled GLs might still be affected by it.