What does a green Send arrow mean in Messages?

So I've been blocked by an iPhone user before. Here are the things I've recognized: -when I call it goes to voicemail -when I try to send an iMessage it sends as text message -usually after trying to send more than one message, the send arrow will turn green instead of blue and stay that way Here is my dilemma. This past week someone blocked me and I send them 2 texts and they both sent as texts and finally the send button turned green. I realized a day later that the send button turned blue so I thought they unblocked me , I sent another message and the send arrows turned green and stayed that way for longer this time but now it's blue again. Wondering if this means I'm unblocked?? I don't want to send another message !

[Re-Titled by Moderator]