Why are some text messages displayed in green and others with a blue font?

[iMore Question]

when i send a text message it sometimes shows up highlighted in green & sometimes it is blue

 

[HankAZ]

when i send a text message it sometimes shows up highlighted in green & sometimes it is blue

I will infer that your question has to do with why are some green and some blue and what is the difference.

Text messages that are displayed in green are texts sent as SMS messages.
Text messages that are displayed in blue are texts sent as iMessage messages, to another iOS device.