Spoiler alert: It’s not because blue matches everything (though it kinda does). “Blue jeans are blue because of the unique dye used,” says textile scientist and denim expert Melanie DiSalvo.

It's also why many jeans are blue on the outside but white on the inside. Each pair of jeans requires 3-12 grams of dye. Each year, we produce several hundred thousand tons of indigo dye.

With the explosion of the youth market in the 1950s, blue jeans went on to symbolize angst (smelling like teen spirit; they looked better unwashed) and cowboy grit—worn on the bods of teen idols ...

Blue jeans through the years — To this day, blue jeans remain the uniform for cowboys young and old. Here, Bruce Beasley and his grandson load cattle on their farm in Patricia, Alberta, in May 2013.

An early pair of Levi Strauss & Co.'s "Duck Trousers" Photo courtesy American History Museum On the 109th anniversary of Levi Strauss’ death, his chief product—blue jeans—have become a $91 ...