First off, what color should the leaves be? I did not take very much notice of what the color was when I got them, but they are currently a bit darker than a lime green. The main reason I'm asking though is because it has two new leaves that have a lime yellow coloration to them.
Is this a sign of too much water or light, or perhaps a sign of not enough light?
Mine was quite a dark green when I got it. New leaves are coming out brighter but darkening as they age. Mine is actually getting a red tint on the dark green leaves which I think is too much light and I've moved it to a slightly shadier position.
I actually went back and looked at the picture I took when I first got it in comparison to what it looks like now. I'm not so sure that the leaves look any different than they did when I first put it in the terrarium. However, I also know that camera colors can change depending upon several factors.
I'm glad to hear that your new leaves are also lighter. Perhaps since I have a few new leaves growing then it's happy.