Does a green bubble mean you've been blocked?

Presumably you refer to the Messages App. No, seeing green bubbles instead of blue does not suggest that you have been blocked by the recipient.

A green bubble simply indicates that the message has been sent using SMS (Cellular Messaging or RCS) instead of iMessage (blue bubbles). Sometimes circumstances can occur whereby a new message cannot be delivered using iMessage - and your iPhone (iPad or Mac) will instead attempt to deliver the message over SMS.

If in an existing conversation, messages will continue to use the last successful delivery method (in this case, SMS). In such circumstances, starting a new conversation from your Contacts list will restore communication using iMessage (blue bubbles).

Zed1947 wrote:

Does a green bubble mean that you have been blocked

FYI, there is no definitive way to tell if you've been blocked.

Green for Greenbacks. SMS may cost you $