The origin of the expression is quite simple: the kings and queens had very pale skin, they were not out in the fields working, and if they were outside at all, they protected themselves against the sun with an umbrella. Through their pale skin they could see the blue veins, however on workers no, due to their tanned skin.
And that's how the expression was born, since the veins were blue and what's inside them is blood, well then the blood had to be blue right?
Good. So on to the next one. I heard this expression, Principe azul, and I didn't understand. What, or who is the blue prince? It's Prince Charming of course! Or the Knight in shining armor if you will. It has the same origin; the blue blood of royalty.
I went online to see what Google would come up with if I searched for Principe azul.
-The one who saves Cinderella, but of course!
Fancy dress for Carnaval?
-Of course... a frog!
Seems the colour blue is not only important in the blood, eh? I like this one though:
|Searching for a green prince, cause the blue one doesn't exist! via|