Comment by cbhl

It's actually supposed to be a pun -- while "green" often refers to the color, it also can mean "young or unripe" (fruit) or "inexperienced, naive, or gullible" (person), such as in the phrase, "a green recruit fresh from college".

I think it's meant more for regulars -- a gentle reminder to be nice in the comments because green users might not be as familiar with the norms -- but I can see how the color choice might be confusing for new users.