IOS 9.3.2 I sent two text messages via Siri dictation. One was displayed in Green with a note saying the message was sent as text. The second was displayed in Blue with no accompanying message. Both were sent by WiFi with Cellular data turned off. Any thoughts on why the difference?
When a message is sent using iMessage, from an Apple device to an Apple device, the message bubble will be blue.
When a message is sent using SMS, in your instance this would be from your Apple device to a non-Apple device, the message bubble will be green. This is to show you that the message was sent but your device can't obtain a read receipt or let you know the message was delivered.
To add to fbara, if there is networking issues an iPhone to an iPhone message can still be sent as a text (flaky wifi) for example.