[Cronos]

In ancient times the Greeks and Romans always described Moors as having dark skin.

I've not seen any description like that -- I'd be grateful if you could point me to some links that say that.

[CobaltBlue]

The very word Moor derives from the Greek maurus, Latin mauri, meaning "dark men." The Mauri were the tribe that lived in Mauretania.

[CobaltBlue]

Here is Caesar calling the Mauretanians "black-skinned." Scroll down to the last sentence, "And I have heard this man say that beyond the country which he ruled there was no habitation of men, but desert land extending to a great distance, and that beyond that there are men, not black-skinned like the Mauretanii . . . ."
http://www.fordham.edu/halsall/ancient/anc-nafrica.html