Lastly, Achilles is never described as having African features so even if some Black people did exist in Greece, that doesn't mean Achilles or any other particular historical or mythological Greek character was Black.
And he wasn't described as have European features.
In the Iliad, Achilles has blonde hair ( = "she (Athena) grabbed Achilles by his blonde hair"; Iliad, 1.197). That's probably the most persistent characteristic given for him and is repeated numerous times. The word "xanth" () used here can be translated as "yellow", "fair", "golden", "blonde".
On the other hand, in Hyginus' Fabulae it is said that Achilles' mother sent him to the island of Scyros, to hide him from the Achaeans who seeked his help in the Trojan war that was about to start. He disguised him as girl named Pyrrha (). This name too suggests that Achilles was blonde or somewhat red-haired, since pyrrhos () means "flame-coloured" or "yellowish-red".
there are black people with blond or red hair
I think you are talking about Australian Aboriginals and not Africans.