Romans \'were not colour prejudiced\', research shows

[Tiberius Clodius Corvinus]

I think in most cultures, now and then, visualisations use almost invariably dark colors and especially black to represent the bad, evil or dark aspects of life. propably a evolutionary heritage as the night / darkness means danger and the unknown to us. this applies for civilizations whose people's skin color is black as well, IIRC. so it wouldn't be surprising that a universal "built-in" bias towards whose people is shown, which people aren't necessarily aware of.