most green zoos prefer to be lower in the tank under MH and some will dull/brown out if up too high. I would put those star green zoos on the bottom and somewhat shaded and they will color back up. From all my fiddling around with all of my different color zoos I find that for the most part; the color of the zoo does best(color wise) with the actual light/depth water penetration. IE.. blues, greens lowest because the spectrum reaches furthest and reds, oranges, pinks highest because that light spectrum does not penetrate the water far. This is just from years of messing around with them and JMHO.
I also feed oyster eggs, phyto and do frequent water changes. I use to not do that many changes in the main tank and some of my colonies started losing some of their sheen. I however did frequent changes on my frag tank and the color was much better on the same zoos from the same colony(same lighting). It seems they use the elements from the water change and it aids in their color. JMHO and good luck!
