I've got a lot of tigers, greens, and albinos. The greens occasionally school with the natural tigers but usually they prefer other greens. Same with the albinos although they seem to never school with the others at all.
I had 7 tigers for awhile 5 normal 2 green and they all schooled fine together but from time to time the greens would go off on there own, but would rejoin soon. I also would say my greens were a little less aggressive.