Isatis tinctoria, known as dyers' pastel, is a herbaceous plant of the Brassicaceae family. This plant introduced to Europe in the Middle Ages by the Moors for its medicinal properties has a particularity: it produces a unique blue-green dye called "pastel". For this, the leaves are crushed, fermented and then rolled into balls called shells or cocagnes. From the 15th century to the 17th century, pastel was used to dye fabrics, fibers and especially royal fabrics with “royal blue”. Its productio