I like the idea that Kryptonite from different universes should affect the different Superman differently. If I were you, I would stick with the basic idea of green Kryptonite. But why not make subtle changes to the shade of green? I really, really like the idea of turquoise Kryptonite. And how about yellowish lime-green Kryptonite? Maybe in one universe the Kryptonite could be basically green, but shimmering with muti-colored opalescence. Then of course you need the bright, unmerciful, neon green Kryptonite.
I *love* the idea that all the Supermen could be unpredictably affected and somehow weakened by the Kryptonite that's not from their own universe. (If it were me, I would, of course, have each Superman affected by one alien Kryptonite substance in such a way that he realized how unforgivable it was that he had been ignoring "his own" Lois as much as he had - presumably the LnC Superman wouldn't have this reaction, though...
)
Ann
