My iphone4 SMS send button has turned blue, it's iMessage, but I turned off wiFi, why is it still blue, and why is it green again?

If you want a message to turn green, just turn off the Internet or imessage.

Iphone has two short message modes, one is ordinary mobile phone short message and the other is imessage network short message. The colors of these two kinds of text messages in the app are different. Ordinary short messages are green bubbles, and imessage is blue. If the mobile phone iphone turns on the imessage function, and the other party is also an iphone, the short message between them will be sent through imessage. It is easy to turn it off. In setting the imessage option, you can turn off sending SMS via imessage. The second method is to turn off the mobile phone network (both mobile phone network and wifi should be turned off), so there is no network environment, and short messages can only be sent by ordinary short messages.