Tut never looked black.
His grandmother sure did. (Tiy, wife of Amenhotep III.) However, there is abundant evidence from ancient Egyptian art to confirm that the Egyptians were not "black." They depicted Nubians with black color. By the time Alexander came along Egypt had been a civilization for more than 2000 years, and an empire by any measure had existed there a thousand years before Alexander. That means far-flung trading networks and that means a diversity of ethnicities; but the earliest depictions of the dynastic Egyptians were definitely not of sub-Saharan Africans.