Blue texts are texts, photos, or videos that you send over iMessage. These texts are sent and received over Wi-Fi or cellular data. Due to that, they won't count against your text messaging plan if you have one for your phone.
Green messages are ordinary SMS text messages, while blue messages are using Apple's proprietary iMessage format. If you're used to seeing blue iMessage text bubbles but they are suddenly green, it can be an indication you've been blocked – but that's just one possibility, and isn't necessarily the most likely.
In general, if your message shows in a blue bubble, it means that your text has been sent to other Apple users. However, if your iPhone messages are green, you may send your messages to a non-Apple user, or there are some problems with your iPhone.
A green text message on your iPhone isn't a sign that your phone number was blocked, or that the text was not delivered. Instead, it means that the message was sent as a standard SMS message rather than an iMessage, which will appear as blue.
Text Messages that use a Blue Bubble indicate thet they were sent using the iMessage service from Apple which uses the mobile data portion of your cellular service. iMessages can be used solely between Apple devices (iPhone, iPad, iPod or a Mac).
The green message background indicates the traditional SMS text message. It actually means a message that you have sent to someone else is through SMS message service instead of Apple iMessage. Blue message background means the message is sent via iMessage technology.
If the iMessage never shows a “Delivered” or “Read” message, and it's still blue, then you may have been blocked – but not always.
If the chat bubble is green, that could indicate someone has blocked you, especially if your chats with this person used to be blue. However, this is only true if both of you use iMessage on iPhones. If the other person switched to an Android phone, their bubble may have turned green (plus, they may have a new number).
The Recipient Wasn't Using an Apple Device at the Time
Remember, iMessage only works between Apple devices. So, if your family or friend switches from an iPhone to an Android smartphone, for example, your iMessage will automatically be sent as a text message to them.
Since iMessage is an internet messaging service, it needs an internet connection to work. By default, when internet signals are weak or unavailable, the iPhone will automatically switch to SMS.
Short answer: Blue ones have been sent or received using Apple's iMessage technology, while green ones are "traditional" text messages exchanged via Short Messaging Service, or SMS. Does this matter? In the grand texting scheme of things, should you care whether your messages are blue or green?
iMessage not saying “Delivered” simply means the messages has not yet been successfully delivered to the recipient's device due to some reasons. Reasons could be: their phone not having available Wi-Fi or cellular data networks, they have their iPhone off or on Do Not Disturb mode, etc.
iMessage is available only on Apple devices through the Messages app. It feels to users like an instant messaging service and is similar to SMS in that the message format looks the same. But iMessage can only be used between Apple users (you can't send an iMessage to an Android phone).
If it's green, it's an ordinary text message and doesn't offer the read/delivered receipts. iMessage only works when you're sending messages to other iPhone users using the Messages app.
Fix problems sending or receiving messages from specific contacts. Delete the contact and add it again. Check if you blocked them. Verify that their phone number is correct.
If your texts are green when sending to another iPhone, it's likely because the message is being sent as an SMS/MMS rather than an iMessage. This could be due to iMessage being turned off, network issues, or the recipient's device not being connected to the internet.
SMS messages don't mean that your name has been entered into a person's blocklist. They simply mean that your messages are not being delivered to the target person. Yes, this does happen when you are blocked, but it also happens when you or the target person has no access to a cellular or Wi-Fi connection.
Another way to know if someone blocked you on iMessage is to check the bubble color. If you see green bubbles, this means that your text messages are being sent through SMS, and they might have blocked you on iMessage.
Blue or Green has nothing to do with being blocked. Blue means iMessage, i.e., messages sent through Apple, Green means messages sent through SMS.
So if the person's iMessage is off, and you try to send it, there name will not appear in blue and a normal carrier text message will go.
A red flag that you've been blocked is when you don't see the delivery status or the read receipt at all. The message you just sent will still be in a blue bubble, but it will have no delivery status below it – not even a "Not Delivered."
Blocked text messages disappear
They won't receive any notification that they're blocked, and their messages will still look like they've been sent. But you won't receive any of them, and you can't respond.
If you see a green message bubble instead of a blue one, then that message was sent using MMS/SMS instead of iMessage. There are several reasons for this: The person that you sent the message to doesn't have an Apple device. iMessage is turned off on your device or on your recipient's device.