IMessage group message? (iPhone)?

I see a lot of other peoples messages, but it almost always gets a new text as if it is from a new sender, it does not remain in the group folder. Also, when i send a message in the group message, the text always shows up in green, not blue as if it was using message.

Any tips?

If someone in the group is away from Wi-Fi or doesn't have an iPhone, their message will be green.
Not sure about the folder issue