While in the past, there was no indicator that one was blocked. However, now when blocked, iMessages go as texts/green. I know this for 100% sure because my boyfriend told me he was gping to block me and after that all of my messages went green/texts. When he unblocked me they went blue/iMessage. I tested it with my son and had the same result. However, if the iPhone loses signal, or was turned off, messages will also go as texts/green. So green texts does not automatically mean one is blocked. But if one IS blocked, messages will not go as iMessage.
Green texts means either one was blocked or the phone does not have service at the moment or the phone was turned off.
It would also appear that after a few hours
Of being blocked, the type line will turn blue again until you try to send another iMessage.
If the phone is still off or you are atill blocked, it will turn green again. Your phone only knows it is blocked for so long. Kind of has to be reminded I guess.
I hope all was worked out. Being blocked is not fun but can bring peace for a little while for all to calm down. Best of luck ...