Egypt comprises of black lands which were productive in Upper Egypt and red lands are dry areas and known to be the Lower Egypt.
King Menes also known to be Narmer was the ancient king of First Egyptian Dynasty who invaded the Lower Egypt which was located under the lowlands of River Nile.
He was accounted to be the first Pharaoh who conquered the Lower Egypt through military invasions. He unified both the kingdoms and wore double crown. White color represented the Upper Egypt and Red the Lower Egypt.
