Jeans Tradition

Dyeing

Traditionally, jeans are dyed to a blue color using indigo dye. Some colors that can be achieved however are pink, blue, yellow, black, and white. These colors are achieved by coloring other fabrics to resemble jeans. Approximately 20 million tons of indigo are produced annually for this purpose, though only a few grams of the dye are required for each pair of these trousers.

Pre-shrunk

In the 1970s Hal Burgess first marketed "pre-washed" jeans. He was a salesman for his father, who owned a large jeans manufacturing company in Cartersville, Georgia. While on a sales trip, there was a flood in the hotel room where Burgess was storing jeans. He asked the hotel owner if he could rent out the pool to wash the flooded jeans. The jeans shrunk but Hal decided to market them as 'pre-washed' jeans and sold them two sizes smaller than they were initially labeled. This was the first time 'pre-shrunk' jeans were marketed.

Source Wikipedia