The continent doesn't have an official flag; the nearest you can find is the flag of the African Union, constituted by all African countries with the exception of Morocco (due to Western Sahara recognition and membership):
I think a new flag is necessary, not only because it's not an official African flag, but because it excludes Morocco. My attempt to the flag of whole Africa:
This flag comprehends the main color sets in Africa: the Pan-African red-yellow-green and red-black-green and the Pan-Arab black-green-white-red. The concentric circles, ordered from the lighter to the darker, represents the sun penetrating the darkness i.e. the peace and glory of the continent that will overcome the dark past of slavery and misery.
Your comment is welcome. Please, leave a comment.
If you see any issue regarding this flag, I'd like to be told. In the worst hypothesis, it's purely my ignorance.