No one really has blue blood, of course, but in the past it was noticed that some people had bluer veins than others. This was spotted particularly in Spain, which was the only country in Europe that had been settled for any length of time by the Moors of North Africa. They conquered and ruled southern Spain for nearly eight hundred years. During that time the Moors mixed with many European Spaniards. However, pure-bred Spanish aristocrats noticed that they had bluer veins than Spaniards from mixed ancestry. So they began calling themselves blue-blooded as a mark of noble birth. In time the idea spread to other countries, where blue blood became associated with the noblest of all the royalty.
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