Does iMessage use up data on your iPhone?

When you text someone, it's green messages. When you imessage someone, it's blue. So when the messages show up as blue, does it take up data?

If you are connected to the Net via wi-fi, iMessage does not use any of your data allowance. If you are connected via a cell connection, though, it uses data.

IMessage works via wi-fi, so no. The only time it would is when you do not have access to wi-fi; it will default to cellular data.

When you are connected to Wi-Fi it will use the Wi-Fi instead of the data.

Blue and green mean something totally different. IF you aren't on Wi-Fi. IMessage and Facetime will use data. They can and do use both. All the blue really means is that you've interacted with another idevice user. IMessage/Facetime goes through Apple's servers, not your carrier's towers. It gets there by Wi-Fi or data, your choice. Green just means you are interacting with a non-Apple device and using data to text like normal. Best luck.