All the genetic diversity that we see today was built in at the beginning. After the Flood, as family groups were isolated by geographical and language barriers, certain physical characteristics began to be expressed more frequently while others were suppressed. Usually these physical differences are very slight confined to only skin pigmentation, hair texture, certain cranial features and eye color. Biologically speaking, all are of the same species, are interfertile and produce fertile offspring. Skin color is due to the variation of a substance called melanin in the skin.
More melanin means more coloration.
Jesus' skin coloration was probably somewhere between black and white, i.e. olive-skinned as are people of the Middle east today. Racism embraces the belief that hereditary biology determines the differences between groups, that cultural differences are predetermined and immutable, and that the distinguishing social and cultural features of the subordinate group are inferior. These faulty assumptions are responsible for irrational prejudice and discrimination. For example, Jews are an ethnic group. They have racial differences.