How is it possible to colour with herbal hair colour without ammonia? Which main ingredient gives colour?

How is it possible to colour with herbal hair colour without ammonia? Which main ingredient gives colour?

Among the organic powders listed on our website: Indigo, Henna, Amla, Walnut Shells, Shikakai, Brahmi, Bhringraj, & Neem – Henna and Indigo are commonly known for their natural hair coloring properties. Henna is a natural dye that has been used for centuries to color hair, skin, and nails. It imparts a reddish-brown hue to the hair. Henna is a popular choice for those seeking a natural alternative to chemical hair dyes. It does not require the use of ammonia. Indigo is another plant-based dye that, when combined with henna, can produce a range of colors, including shades of brown and black. Indigo also does not require the use of ammonia.