I want to continue to use my iMessage
I don’t know what happen to my iMessage it show green color
Question marked as
Green means either you or your recipient do not have an internet connection and cannot send or receive blue iMessages.
There's nothing specifically wrong with that. If the other person does not have an internet connection, then the message will be send as a traditional SMS.
click here ➜ What is the difference between iMessage and SMS/MMS? - Apple Support