How long ago was this ?
I hope that was the comic I saw !
or another childhood memory shattered !
It was in 2002. This is the only thing that I can think of that may give the impression that a gay GL was shown. There are about 5 human Green Lanterns and they have all been shown to be straight. Some have had relationships with aliens who were clearly female, but not gay relationships.
I can't even recall a gay alien GL, though some of the aliens may not be of any particular gender (may reproduce asexually).