Do iMessages cost when sent internationally?

I live in Alaska and I'm texting a friend in British Columbia. We both have iPhones and we have been texting using iMessages. Will this count as international texting or towards my data? The texts are always blue, not green on our screens. My network is AT&T.

No! I text my friend in Germany all the time! IPHONES FTW!

No, blue = free Make sure the option in settings is off where it says "send as normal text when imessage not available" so it doesn't accidently send in case imessage is down for some reason.