"Yet there are grounds for thinking that the Greek tradition was substantially correct. For Manetho, our highest ancient authority, definitely affirmed that in the city of Ilithyia, it was customary to burn alive 'Typhonian men' and to scatter their ashes by means of winnowing with fans.
(Plutarch's Isis et Osiris 73).

These 'Typhonian men' were red-haired because Typhon, the Egyptian embodiment of evil, was also red-haired (Plutarch's Isis et Osiris 30, 33). But red-haired men would commonly be foreigners, in contrast to the black-haired natives of Egypt; and it was just foreigners who, according to Greek tradition, were chosen as victims. Diodorus Siculus points this out (1.88.5) in confirmation of the Greek tradition, and he tells us that the red-haired men were sacrificied at the grave of Osiris, though this statement may be an inference from his etymology of the name Busiris, which he explains to mean 'grave of Osiris'. The etymology is correct, Busiris being a Greek rendering of the Egyptian Asir 'place of Osiris."
[Apollodorus, Library and Epitome
(ed. Sir James George Frazier) 2.6.8]