Green is gorgeous and perfectly fine.
I don't get this too sheer/showing leg type thinking- I want my guests to look attractive and have fun, not be wearing knee length skirts at an 'appropriate length'.
I find the wedding 'rules' really weird on MN, and I've never heard of any of them, except perhaps the don't wear a long white dress (although as a teen I wore a short white dress to a wedding and no-one fainted, it was pretty obvious which one was the bride).