Alkanet root is well known for its pigmentation properties. Dried herbs like alkanet root are primarily used for dying wood, fabrics, and the like but also are popular as a natural dye in soaps. The whole root is ground and then mixed with other products or oils to colour them. As far as herbs go this is one of the most sought after for its coloring properties. It is commonly used in soaps, lotions, and make up products.
If using in soaps, lotions etc. it's usual to steep the cut or ground root in warm oils until the oils takes on the colour, then strain the particles from the oils and make your soaps or lotion etc. with the coloured oils.