Except your Egyptian Pharaoh was Greek and didn't ride around in a chariot. RS2 has the Galatians as an actual faction.
I'm well aware the Ptolemies are an incestuous pile of Macedonians, but they still stylized themselves after Kemetic religious traditions — king worship and all that — and understood themselves as the monarchs of Egypt. What's your point? If anything it just affirms the idea that people get around.
(No one said anything about fucking chariots.)
People definitely did get around, but it's always a question about who these people were and where they went.
Apart from some Nubians fucking around in Egypt, you never had blacks interacting with whites in any major way until the 19th century's scramble for Africa, with some minor exceptions (black slaves in medieval and early modern muslim Arab countries, but they were a small minority; religious conversion efforts by Christian ans Muslim missionaries in African kingdoms in the middle ages), so that's why the whole negro soldiers in the Roman Republic is such an annoying thing.
With pretty much every major population movement, we have at least a rough idea where they came from (even the Huns who are largely a mystery!), where they went, and why they went there. We're also roughly aware of the numbers involved: Alexander brought Hellenism all the way to the border of India, giving birth to cool cultural phenomena like Indo-Greek stuff, but that doesn't mean there were millions of Greeks suddenly colonizing eastern provinces: he had an army, and some of those men settled in the areas he conquered. Not enough to replace the local population, but enough to have a cultural impact and to marry and mix with the local women, while still staying a minority-in-power.
Egypt is a great case study because it was first conquered by the Persians, and then by Alexander, and once the Ptolemaic dynasty took over there was barely any trace left of the Persian rule, since the Persians didn't do much other than assign a Persian Satrap to the province. There wasn't a Persian population to speak of, other than some traders settling there for the purpose of trade. Meanwhile there has always been a small Greek minority along the coast thanks to Classical Greek colonialism, which consisted of a bunch of Greek settlers fucking off from their home Polis and founding a new one somewhere on the coast.
Also, it has to be kept in mind that most of these people were Caucasian sub-races. Celts and Germans? They're paler and blonder than the Mediterraneans but other than that, they don't look too different from your average Roiman. North Africans? They look like more tanned Romans. Carthaginians are west semitic (Phoenician colony), and look pretty much like people in the Levant... and Syrians even today don't look too different from Europeans.
Really, when it comes to unit models you shouldn't be able to tell much of a difference when it comes to skin tone. Soldiers recruited in Africa should be more tan, yeah, but then when you send a German to Africa and let him serve there for 20 years he's gonna get tanned too.
You might get some noticeable skintone differences when you enter India, but the India that the ancients interacted with is northern India, which has always been the center of the Aryan Indian civilizations, while the dravidian south - where the brown people are - wasn't really in anyone's picture.
Even in the huge multicultural Persian Empire, subject populations were characterized through their hairstyles, clothing, and mannerisms rather than their skin tone or facial structure or anything.
In Roman ethnographic texts, whenever they encounter a people that is not Caucasian, they find their features to be so strange they have to mention them as something strange and foreign, like the descriptions of the Huns (which most Roman authors considered to be barely human).