What does it mean that Apple's mobile phone 6plus sends a text message to display the blue font?

Blue information indicates that you are all using iMessage service; Need data traffic, so it is still free.

On the iPhone, when the text bubble is blue instead of green, you know:

I use iMessage instead of SMS, and SMS conversation is free.

The SMS has been sent to all Apple devices of the other party, and the other party has received your SMS.

This will let the SMS controller who uses the SMS service know that his face will turn green with jealousy.

IMessage is an instant messaging software launched by Apple, which can send short messages, videos and so on. It has high security. IMessage is different from SMS/MMS service of operators. Users only need the data support of WiFi or 3G network to complete communication. IMessage uses the new message reminder system of iOS and Mac os to directly push information to the other party's screen, regardless of whether the other party is in the game or locked. If both parties are using iMessage, you can even see the state of each other's speech.

Wish you a happy life!