Mahatma Gandhi in 1917 undertook a Satyagraha against the British policy of forcing farmers to grow Indigo plant. Indigo derived from the Indigo plant was used in the textile industry to impart a blue color to fibres.
What type of a substance is Indigo?
Dye
Indigo is a dye. A dye is a colorant that gives color to cloth and fibres. Dye Indigo imparts a blue color that is often used to dye blue jeans today. The picture below shows Indigo dyed yarn.