The plant has a root of blackish appearance externally, but blue-red inside, with a whitish core.

The root produces a fine red colouring material, which has been used as a dye in the Mediterranean region since antiquity.

It is used to give colour to wines and alcoholic tinctures, to vegetable oils, and to varnishes.

[3] Alkanet is also traditionally used in Indian food under the name ratan jot, and lends its red colour to some versions of the curry dish rogan josh.

In alkaline environments, alkanet dye is blue; in the presence of acids it gradually changes to crimson.