Why did my text send green and say delivered as text message

If you were sending to another iOS device, it could have been that one of you were having issues with your iMessage. It could have been you, the sender, or the receiver. Could have been a bad internet connection, out of wi-fi range, or anything that would have interrupted the internet connection.

That is also true. You made it sound as if you were unaware of why it looked that way since it was green. That is what happens when you send a text (SMS) or as I described, an issue with iMessage if the recipient is an iOS user.