We had to get it out of the way so we could move on.
Originally, the Guardians imprisoned Parallax, the entity of
fear, in the central power battery of Oa when they were learning how to wield
the power of will. This caused all of the Green Lantern rings and corpsmen to
have a susceptibility to the color yellow, no matter how trivial the color's
appearance. Of course, this fact didn't come out until sometime after the
mid-90s and the "Emerald Twilight" arc in Green Lantern when Hal Jordan drained the
central power battery and a new ring--sans yellow impurity--was made for Kyle
Rayner.
Still, the impurity was around for the better part of 44 years
before being taken away and later explained as a part of the Parallax problem
after Green Lantern:
Rebirth. It still makes its way into fandom jokes, like in Frank
Miller's All-Star
Batman.
