I made this version based off of the original Anime (I have never seen the new anime so I do not know what he looks like in it) where his hair is green so it isn't a matter of whether he should or should not have black hair - it is all up to the version I decided to make as well as my interpretation of what his hair colour really is I prefer it as green because green is the colour of Envy and if you pay close attention to the characters closesly, they bear some colour representation of their sin. For example, not only are Lusts' eyes red, but her dress (though black) has a red tint to it.
I've read the manga and I heard that the new anime is pretty much the manga and I don't really have the time to. Especially since I have read the manga and watched the original anime, there are other manga/anime I would like to get to that have been on my list for a while now
Read it - it's really good! I prefer reading over watching anime and it's generally what I do. If an anime has no manga then obviously I have to watch it, but I don't watch too much anime - it takes up too much time and I am a quick reader, plus you get all of the authors information that is left out of the anime - you get the real story with no fillers.