The best natural hair dye is 100 percent pure henna. Pure henna is made from the leaves of the henna plant, which people have used since ancient times to color hair and skin naturally.
Pure henna tints the hair naturally by staining the hair strand with the tannins, or dye compounds, in the plant. Henna blends away gray hair and provides a reddish tint to the hair. It doesn't lighten the hair, but it does make the hair shiny and reflective, giving the effect of natural highlights. Henna is the only long-lasting, natural hair dye that exists. It does not wash out of your hair, nor does it fade. Those who have gray hair need to only retouch the new growth.
There are some companies that add other compounds to their henna for different shades or faster processing time, but some of those ingredients, such as metallic salts, are damaging to the hair. Only 100 percent pure henna gives the results described above.
Other natural dyes include those that are vegetable-based. Many of these come in bright or creative colors, such as hot pink or blue. They condition the hair while adding color; however, the color is not meant to last a long time. These colors often wash out after a few weeks, because they are made to be temporary. Vegetable-based dyes can be a good way to play around with different colors before you decide on a permanent color.