Apple phones will reply with blue and green messages, such as success or failure.

IPHONE supports two SMS modes: one is based on communication network mode, which is commonly understood as SMS mode. When the mode is successfully sent, it will display green; The other is the IMESSEGE mode, which is not a communication network, but a data network (i.e. wireless network or WIFI). After the transmission is successful, the mode displays blue. After successful sending, the former charges the SMS fee, while the latter charges no SMS fee and takes up traffic (if it is WIFI, it charges nothing, but takes up your broadband traffic). The latter is more economical, but it should be noted that only when both parties are Apple devices can they be sent via IMESSEGE, otherwise they can only be sent via SMS. In addition, if the SMS is not sent successfully, it will be displayed in gray. In this case, you are obviously sending SMS in the form of IMESSEGE.