Short answers, pulled from the story.
The first blue pigment ever created by human hands appeared in the third millennium BC. Egyptian blue was produced by heating pulverized sand, copper, and natron to create the first artificial colorant in history.
A German druggist named Johann Jacob Diesbach discovered Prussian blue in 1709. This pigment arose from experiments involving heating dried blood with iron sulphides and was initially called Berliner Blau.
Blue eyes appear blue due to an optical effect called Tyndall scattering within the stroma of the iris. The irises of people with blue eyes contain less dark melanin than those with brown eyes, which reflects short-wavelength blue light to the viewer.
Shuji Nakamura of Nichia Corporation demonstrated high-brightness blue LEDs in 1993. Nakamura was awarded the 2006 Millennium Technology Prize for this invention and shared the 2014 Nobel Prize in Physics with Isamu Akasaki and Hiroshi Amano.
The Prince-Elector of Brandenburg, Frederick William I of Prussia, chose Prussian blue as the new color of Prussian military uniforms in the 17th century. This uniform was worn by the German army until World War I.
Blue eyes are most common in Ireland, the Baltic Sea area, and Northern Europe. In Estonia, 99% of people have blue eyes, while in the United States, 16.6% of the total population had blue eyes as of 2006.