Natural Blue Dye, Isatis tinctoria 50g Hazard warning: May cause damage to organs through prolonged or repeated exposure. Do not breathe dust. Get medical advice/attention if you feel unwell. The import of indigo from India was very expensive and laborious before the discovery of the sea route by Vasco da Gama, and as a result, the production of the blue dye from woad developed in Europe. With the sea route and the cheap import possibility of the indigo from India to Europe, the woad production in Europe ended. Woad indigo differs from true indigo by its more grayish hue.