New account, IIRC less than 2 weeks old. The name is colored green. But I've seen it not be consistent, where some posts are green, others aren't. All in the same thread.
It's more complex than just creation date. Somewhere in there it involves votes cast on your posts, which is why you might see someone's name switch colors from one post to another in the same thread (the system doesn't go back and switch name colors on previously-created posts). IIRC the exact mechanism isn't public.
New account, IIRC less than 2 weeks old. The name is colored green. But I've seen it not be consistent, where some posts are green, others aren't. All in the same thread.