I was kind of surprised when I first learned that the first of the post Julio-Claudian emperors were probably pretty dark skinned, and that later emperors from North Africa and Syria were probably darker skinned still.
A lot of people who know a little bit about the Roman Republic presume that insular values about citizens of the city remained universal later on. It’s easy to see why they would do that, given how Republican-era Romans tended to be all about valuing old families who could trace their roots back to the times of the kings, and who were probably very white.
But by the end of the first century CE, all that had definitively changed. The Romans ruled a vast empire with people of many different ethnic origins, and they behaved that way.
No longer was Roman citizenship reserved for old families. No longer did ancient families hold on to power for themselves.
Romans of the 4th and 5th century wouldn’t have known what multicultural meant, but we would certainly view them as an intensely multicultural people.
And for those who believe that the Romans in Britain were lily white, it’s kind of amusing to note that when the western empire was fighting off barbarians in the 5th century, those barbarians really were pretty much lily white, while many of the Roman soldiers facing them were dark-skinned.