I planted java moss on a log in my viv, and its taking off like crazy!It grows incredibly fast for me right now, faster than any other plant i have in my viv right now
It's only been in there for like 3 weeks too!
I think its a really light green because of how close it is to the light. The java moss i have at the bottom of the tank inside a monkey pod is a darker green, but is also growing slower.
Since you were talking about doing a moss carpet, i thought id post pictures of the NEHERP Moss that i planted a month ago. It's not so lush right now, but about a week ago, a whole bunch of new little growth points started popping up everywhere!

So it should be a nice lush carpet in a month or so! Here's a pic of the all the growth points im talking about:
And again, i have the same NEHERP Moss on a higher ledge, and it is growing much faster (and a lighter green color) than the moss growing on the bottom.