Why is it said royals have blue blood?

Answer 1

If you look at the wrist of an untanned caucasian person, the veins there look almost blue. Royalty were usually shaded when out in the sun, by servants and the like. Thus, royalty were believed to genuinely have blue blood.

Answer 2

The ordinary workers, like farmers, were tanned because of staying on the field every day.

Therefore being light-skinned was a sign of royalty.

The blood vessels of light-skinned people look blue under light, so 'blue blood' was a sign of royalty.

Answer 3

No people just say that because the royal family are special