Odd side-note, but the reason for the term "blue bloods" actually has to do with the use of Colloidal Silver, one of the earliest antibiotics. Well, although in the 19th century it became a common practice to fight infection with colloidal silver, due to it's high price, only the rich aristocracy could afford such a high-priced treatment. Even before it became a common practice to treat with colloidal silver, rich families often owned a lot of silver utensils and wares for food, and would end up ingesting a decent amount of silver. That silver turned their skin blue, usually only in areas closest to blood vessels, but in some cases it would be visible in the face, eyes, and mucous membranes. and so the rich aristocracy became known as "blue bloods".
RE: The Psychology of Colours (Part 3) - Cool Blue