Copy the text (you want to make appear in green).
THEN chose post number you want to reply to.
It will appear in the box with an ">" before the sentence. It will be black, until you hit "New Reply" button.
Then it will appear in your new post in green.
If you want to start a post (not a reply), you can put an arrow (">") before a word or a sentence and it will be green, after you sent it.
If you want, you can do a "test reply" to me and see if I explained it correctly or sufficiently.