You don't need to read anything related to skin colour because that is already provided in the Roman and Greek images of the people showing them as dark skinned so Romans calling them Afri and depicting them as nubian/black means Afri-Terra is Land of the Blacks, they gave race a name instead of calling them by description so essentially you can just add people after the word black if you want to nitpick.
You do need to read something related to skin colour if you're claiming it to literally mean "land of the blacks" though, otherwise it simply doesn't. Especially since you yourself earlier said that it was the name given to a group of non-Egyptian black people, meaning the Romans wouldn't have even considered all black people African, only those that were actually part of Roman Africa.
It's not nitpicking, it's pointing out that there's no evidence it was named "land of the blacks" rather that it was just named "land of the Afri people (who happen to be black)" in the same way that England originally meant "land of the Angles (who happen to be white)" but nobody would ever claim England meant "land of the whites".
If there is any evidence that "Afri" meant black in any of the local languages, then fair enough. But otherwise there's no evidence to support that claim.