Slavery was a vital aspect of ancient history. It is missing in the game. There should be prisons and camps for slaves and prisoners of war. Also, there are no bars, restaurants, nor are there whore houses. All these things are missing.
This is not a reason to skip this. They don't skip it in other forms of art, e.g. movies or literature. Why should it be skipped in a game in which it even wouldn't be a point of discussion, because it simply displays history without any personal comment. Political correctness is idiotic. Because a historic fact can never be politically incorrect. It's simply history, that's all.They will never touch these grounds. There is no denying that slavery (whoring as well) is part of nearly the whole human history. In fact, EVERY super power of the past and of today used this kind of forced labor to pave their way to greatness. But history-accurate as it may be, this is very sensitive topic to be included on a mobile game intended for a wide audience. To avoid hatred, debates, lawsuits and other possible harms, the smartest move of the devs is to skip this boatride.
Any color, depending on chosen culture and warfare. Just as it was in history.The whorehouse could give a moral bonus to troops. What colour would the slaves be?