What is what does it mean when iphone messages turn green?

When iPhone messages appear in green instead of blue, it indicates that the message was sent as an SMS/MMS message instead of an iMessage. This typically happens for a few reasons:

• The recipient is not using an Apple device: iMessage is exclusive to Apple devices (iPhones, iPads, Macs). If the person you're messaging has an Android phone or another non-Apple device, your messages will be sent as SMS/MMS.

• iMessage is disabled on your or the recipient's device: If iMessage is turned off in the Settings app on either your phone or the recipient's, messages will default to SMS/MMS. You can check this under Settings > Messages > iMessage and make sure the iMessage toggle is on.

• The recipient is not connected to the internet: iMessage requires a Wi-Fi or cellular data connection to function. If the recipient has no internet access, your message will be sent as SMS/MMS.

• You are not connected to the internet: If you have no Wi-Fi or cellular data access, your iPhone will attempt to send the message as an SMS.

• The recipient's phone number is not registered with iMessage: There might be a problem if the recipient recently switched from an iPhone to a non-Apple device, it might take a while for the phone number to be unregistered from iMessage.