I always kind of liked the X-Men years where they all wore matching outfits. It was a good look. The JLA has such iconic personalities, though, that I wonder how it would look to put them in matching outfits. Plus DC hasn't been as crazy with the various costumes like Marvel has for its big guns. There's a reason why Spider-Man didn't lift too many eyebrows when they put him in the black-and-white FF uniform--he'd already worn so much before that. But imagine putting Green Lantern in a different color? Doesn't quite work. What color scheme would you go with for such a design?
I'd probably just go with Black/Navy/Yellow, mostly because we know Batman looks good in it:
But GL would probably look a little weird, and I suppose that look might be a bit dark for the JLA.