Before I start, take a look at the flag below.
Flag of the Tripolitania Vilayet (1864–1911)
No, it's not a joke.
It is a real historical flag of Libya, which was in use before it was colonised by Italy in 1934. Back then, its official name was Ottoman Vilayet of Tripolitania.
Now, take a look at another historical flag of Libya.
Flag of the Great Socialist People's Libyan Arab Jamahiriya (1977–2011)
That single-coloured flag above was used during the entirety of Muammar Gaddafi's reign. After Gaddafi was toppled in 2011, the National Transitional Council decides to readopt their old flag, that is, the more beautiful-looking flag that is used today.
Flag of the National Transitional Council (2011-present)
I have nothing against the colour of green, except for the fact that plain coloured flag reeks of dullness. Looks so uncreative. If green truly is the holy colour of Islam (which was allegedly the reason Gaddafi used the colour for the flag in the first place), why not beautify it with some stripes, or different shades of green, or add some crescent and star symbol?
Or add some Qur'an verses, such as in the case of Saudi Arabia.
Flag of Saudi Arabia, wherein is inscribed the shahada (Islamic declaration of faith)
It seemed as if the entire government under Gaddafi administration did not graduate from primary school...even today, I dare bet that I can pick any primary school anywhere in the United States and have at least 20 pupils draw a better-looking flag than that.
If I could pick the best flag for Libya, it would be the flag that has light blue field and a green palm tree in the centre, with a white star on top of it. Such a flag was used by Libya under the historical name of Tripolitanian Republic.
Flag of the Tripolitanian Republic (1918–1923)