In the second half of the 19th century, scholar William Gladstone noted that the color blue is never mentioned in Homer's The Odyssey, in which the sea is described as "wine-dark." Following up on his work, philologist Lazarus Geiger studied works like Icelandic sagas, the Koran, ancient Chinese stories, and an ancient Hebrew version of the Bible, and again, no mention of blue was to be found. 

Geiger looked to see when "blue" started to appear in languages and found an odd pattern all over the world. Every language first had a word for black and for white, or dark and light. The next word for a color to come into existence — in every language studied around the world — was red, the color of blood and wine. After red, historically, yellow appears, and later, green (though in a couple of languages, yellow and green switch places). The last of these colors to appear in every language is blue. The only ancient culture to develop a word for blue was the Egyptians — and as it happens, they were also the only culture that had a way to produce a blue dye.

Without a single mention of blue, the question then became whether ancient people could actually see the color. To determine if people are capable of distinguishing blue without having a word for the color in their language, researcher Jules Davidoff conducted a test with the Namibian Himba tribe, who fit the qualifications to this day.

 When shown a circle with 11 green squares and one blue, they could not pick out which one was different from the others — or those who could see a difference took much longer and made more mistakes than would make sense to us, who can clearly spot the blue square.

Vidipedia/Himba color experiment

So did these people not see the color blue, or did they just not understand that they were seeing the color blue? Is there a difference? Head over to Business Insider to read more.