If my imessage sent green right away does that mean I was blocked?

I sent a picture in a group message. As I pressed send, the arrow went from blue to green. I have read online that usually it will send blue and then after a few minutes turn green if you are blocked. I have identified the person who's causing this. All my previous messages with them have been blue. Now, when i start a new message and begin to type their name in the contact field, it shows up green, even before I send it. Would this occur if I was blocked or is it more likely that they got a non-iphone?

It could mean that but it could also mean:

- They don't have an iPhone
- They're on Airplane mode
- Have iMessage disabled
- Have no Wi-Fi or data to receive iMessages