I lived in Hawai’i for three years and remember blue stop signs, but not green. Green road signs in Hawai’i would fail to stand out for 3/4 of the year and defeat their purpose.
It could possibly be a stop sign from Ko Olina on O’ahu, but I never spent enough time there to actually absorb the color of their road signs.
Is this photoshopped or is there really a country where the stop sign is green? (endlesstalk.org)