There's a green zinnia that isn't too bad, but as a rule I don't like green flowers. A few in a mixed bouquet wouldn't be too bad. Green orchid? no thank you. I think flowers should be pink, red, lavender, yellow or orange. Maybe blue. White's OK, too.
When I was a kid of 10 or so, roaming the woods, I found a green flower growing wild. I didn't know what it was, and that was way before cell phone cameras and google, so I will never know what it was. It looked vaguely like bells of Ireland, if I remember correctly.