How can I know that iMessage is active? If I see such keyboard (please, take a look on the image below), am I right with that: iMessage is active?
The upward pointing arrow in green circle indicates that the message will be send as SMS and not as an iMessage. The name/contact of recipient must be green too.

For iMessage the name/contact would be blue.


Contact shown in blue, registered in iMessage:





Contact shown in green, not-registered in iMessage, will be sent an SMS: