It wasn't that clear cut back then. In Spain, you had the Germanic Visigoths, the Basques, the local Spaniards, etc. all looking a little different and not intermarrying. Then Islam took over for like 700 years, the North Africans raped an enormous number of women, intermarried with the locals and converted many Christians to Islam to avoid the extra taxes. The concept of being white in Spain/Italy/Greece is much more dynamic than with the Anglo-Saxons. After centuries of intermixing you in many cases you couldn't tell who was who just because of their skin color. The problem persists to this day.