Black is in quotes as the concept of Blackness as we know it did not really exist until the seventeenth century.
Here's a recent thread on the topic, with links to older ones.
A summary of the ideas:
Egypt was at the crossroads of several other influential cultures and did engage in exchange with them. A homogeneous society would be unreasonable to expect.
Egyptians viewed themselves as distinct from the Nubians to the south, and the rest of Africa. Afrocentricism often involves some idea of a pan-African culture, and placing Egyptians into this goes against their own sentiments, appropriating their culture and achievements in ways they probably wouldn't have appreciated. It actually downplays the enormous cultural and ethnic diversity of Africa. Imagine if 2000 years from now someone said that a hipster in Seattle and a rancher in Dallas had basically the same "American" culture.
A few studies have indicated prevalence of certain genes common to the rest of Africa in a few mummies. These studies were not extensive and simply borrowed data from studies for another purpose. However, this does not indicate anything about skin color, and even if did racial and ethnic boundaries are not exclusively based on biological differences. England and Ireland are quite different, but both are as white as can be.