iphone "message send fail" BUT also says "sent as text message" - which is it?

I've had "message send fail" in the past, and when I tap on the exclamation mark, it's easy to resend.

I've also had text conversations with people on iphones where the message is sometimes "sent as text message" and so appears in green not blue (not sure what this means, whether it's over wi-fi or not, but as they always got and replied to the message, I'm not particularly fussed)

But the last twice I tried to text one particular contact I've had the exclamation mark that says "message send fail" and also the green "sent as text message". I've never before had the combination, so I don't know how to tell if the message has been sent or not. As it's a work contact, I don't want to text multiple times but also don't want them not to get the message.

Can anyone tell me whether the messages have been sent or not? I'm in the UK and I'm on Orange if that helps...

Thanks in advance!