I repeat: you do know Cephren was black, right?
Curious, Is there scientific proof for this twice-repeated dogmatic statement?
Because Cephren -- better known by his actual name Khafra
-- reigned some time during the 4th dynasty, between about 2400 and 2700 BC. Not only would this put it about 5000 years prior to significant Arab colonization of the region, it's also about a thousand years before Egypt had any significant cultural, economic or military exchanges with European or middle eastern cultures (e.g. the Macedonians, the Persians, the Ptolemics, etc). Their closest neighbors and primary trading partners were the Nubians and the Ethiopians and to a lesser extent the Sudanese. The reason Egypt is predominantly Arab NOW is because the Arabs spent a thousand years doing in Egypt what they've only recently begun doing in Sudan. Or, at the risk of oversimplification, they raped all the women and raised the children themselves (a similar thing happened in the Arab conquest of Spain). Prior to at least the Macedonian conquest -- if not slightly earlier -- the Nile Delta civilization wasn't genetically all that different from any other African nation; their CURRENT racial identity is a kind of genetic trailmix with contributions of everyone who ever conquered the place, and that's a VERY long list.
What are you asking for, though? A genetic study proving that Khafra was actually black? You might as well ask for scientific evidence that Caesar was white.