Is there a group of original black Egyptians?

Yes, there are numerous Egyptians whose ancestors are Egyptians for as far back as they can recall and are Black, especially in the south of the country.

However, it should be made clear that not all or even most of the Ancient Egyptians would be considered "Black". Most had Mediterranean coloration. This coloration varies, but includes colors that might be mis-identified with a Southern German at their lightest and may be mis-indentified with Pakistani at their darkest. Nationalities with similar complexions include most Arabs, Southern Italians, Southern Spaniards, Turks, and other North Africans. Most of these groups are characterized as "White" by the United States Census Bureau, regardless of how others may see them.