What's the green flag indicate?

Attended Lions game last week and noticed the TV timeout official now raises a green flag for a short period of time (maybe 30 seconds) then lowers it while remaining on the field until the TV timeout is ended. I was just wondering about the significance of the green flag. Can anyone explain?

he signals TV timeout. I think he comes out for a booth review as well.

Yes, I got that he signals a TV timeout from his title as TV timeout official, which is what I referred to him as in my original post. What I was asking is, what does the green flag indicate? I have been to many games over the years and I have seen this guy a lot and never before has he waved a green flag. So I am curious as to what that is for.

green flag means he is a rider fan