i sent an imessage to ios user but it is green

There are a number of reasons why that could have happened. If you check your Settings, is iMessage activated, no errors? Have you been able to send an iMessage to anyone else today? Are you connected to cellular data or wi-fi? If everything is okay at your end, then it is possible there is a problem on the receiver's end. They need to have all the same things working to be able to receive correctly too.

If the receive blocks you, you have no way of knowing. There is no outward appearance on the iPhone.