Why do some short messages have green words and some blue words?

The blue background content is a message sent or received by users through Apple's iMessage service, while the green background content is a traditional short message received or sent through SMS.

1, send and transmit standard SMS messages through the same language network as when calling. In previous years, operators charged according to the number of short messages (for example, a short message 10 cent). Later, the operator bundled a certain number of short messages in the user's phone bill package, that is, as long as the number of short messages sent by the user does not exceed the specified number, there is no charge. At present, most telephone packages offer unlimited SMS service.

2. During this period, Apple launched iMessage service, which is similar to the standard SMS service, but the former relies on data network (cellular or WiFi). Apple's iMessage service provides users with two major benefits: first, you don't have to pay the SMS fee to the operator; Secondly, users can experience more SMS functions.