Slavery can exist without racism, which certainly appears and endures in societies without slavery. Slavery and racism become entangled in color symbolism and color prejudice across the planet, and no natural rules determine how hierarchies evolve privileging some people over others. Nevertheless, looking at attitudes toward blackness in medieval Europe shows how one region’s societies evolving attitudes about color and the human family preordained how Europeans treated people who appeared different.Judaism, Christianity, Islam, and pagan antiquity bequeathed to medieval Europe systems of slavery as well as ideas on a hierarchy of “races” privileging some groups and colors over others. The premodern science of physiognomy legitimized constructs of race and color symbolism, to which commentators on the Bible contributed. The apparently stark contrasts among black, brown, red, and white people became proxies for good and evil and other traits. In Europe blackness normally defined Satan, bad things like death and melancholy, and eventually a prevalent type of slave. Color (and gender) of slaves in the late medieval Mediterranean markets affected their prices and revealed buyers’ preferences. Fifteenth-century encounters with sub-Sahara Africa illuminate how Europeans imposed their values of color prejudice on peoples who did not share them.