Yeah, I thought that one was a little iffy. Green isn't a noun, it's an adjective. I wouldn't say the only thing on the outside of my car is white. Asking what is the only color on the flag would make more sense to me, but then again, flags have never been my thing. It was probably an easy answer for the vexillology crowd.
Can you please accept alternate spellings for Gaddafi's name? I tried "Gadhafi" at first, which is also a pretty common spelling for his name. I also know it's sometimes spelled with a Q instead of a G (so Qaddafi instead of Gaddafi).
Maybe it should ask what is the only color to appear on the flag. I assumed a thing would have to be an object on the flag, so I guessed star, crescent, stripe, and other likely objects to appear on a flag. I would argue that Libya's old flag had no objects on it.
I personaly know many people form Serbia who worked in Libya during the Gaddafi era. Common workers of many Serbian construction companies. All of them have the same story. And the story is: People in Libya are very happy because they have everithing they need and they live in peace.