That is why members of noble families are said to have blue blood.
The term they used, sangre azul (meaning blue blood), comes from the fact that the veins on their fair skin were noticeably blue.
This is how members of aristocratic (noble) families are called. For several centuries, from 711 to 1492, when the dark-skinned Maori ruled Spain, members of old Castilian families spoke with pride that their blood had not been contaminated by the Maori or any other foreign matter.
The term they used, sangre azul (meaning blue blood), comes from the fact that the veins on their fair skin were noticeably blue. Namely, the white Spanish aristocrats, descendants of the old Iberians, unlike the others, with the Arabs and other races of mixed inhabitants of Spain, had blue veins on their hands, so the expression blue blood was created on that basis. Later, all nobles and members of noble families (counts, barons, marquises and others), whether white or dark-skinned, began to be called people of blue blood.
Another explanation says that the nobility during the feudal era mostly lived indoors and had a pale complexion which made their veins very visible, unlike peasant-serfs who worked in the open, cultivated the land and raised cattle and therefore their skin darkened on sun and hid the blue color of the veins.
The third explanation is related to the frequent presence of hemophilia in noble, ie royal, families, due to which many subcutaneous hemorrhages occur, which can cause large bruises.
