The color of this plant was apparently bright red when it was collected, from growing in full sun. It went lime green in moderate to high lighting in the aquarium, and in low light, it will become very dark green. So, the color change is related to lighting intensity, and likely heading back to its bright red coloration. It will be cool to keep tabs on!
HD, I don't think that you are that far, even. Lets see what this ends up looking like in a few weeks and we can go from there. I doubt that it will look this nice for most people; it will likely look bright green with a slight red blush on the tips of the leaves.