Just did a google search on this plant, seems like it's a very difficult plant to keep. OVT here on the forums seemed to have good luck with it, here is the link to a short thread about it. Nesaea Red - some observations and pictures
You shouldn't take life to seriously. You'll never get out alive.
Same thing happened to my Rotala Colorata. First few days, it was growing great. Red leaves and everything. Then my tank had a bit of green water attack it. That along with some surface film, the light was just being reduced way too much, and the leaves went back to a green color and looked a bit stunted.
I've found that high light + the right amount of co2 really helps.
plants that are naturally red, will stay red under decent lighting
plants that can turn red will do so when stressed by too much light.
either way, most plants that can turn red, or be red. require good co2 levels to do so ALONG WITH PROPER LIGHTING
rotala colorata is a light responder, and generally does turn red when floating close to the surface
the most you can generally hope for for this plant, is a pinkish underside, and a tanner looking top leaf. with a red stem