Many people (including myself) use natural plants to color thier hair, such as Henna (for Orange/Red color, and adds brilliant shine to hair), Henna with Indigo (to achieve brunette to black colors), and Cassia; a plant that can be used to add shine or add a bit of golden color to very pale blond or white hair. There are other plants and spices that can enhance tone as well. (for more on this, read on)
About the results: I am a dark blonde who used to lighten my hair. I have colored my hair all types of ways, and most recently I decided to 'go dark'. Well, I can tell you that nothing colors and strengthens my hair like the henna. And I now use the henna + indigo mix to achieve a very exotic dark color, that fully saturates (dyes used to wash out easily), shines, and is actually healthy for my hair! The shine you can achieve with the use of henna is head-turning and like no other. Henna binds with your hair, so it is much different than a dye. You can also use chemical lighteners or dyes over it, or apply it over chemically dyed/lightened hair, and as long as you are using PURE henna, you will get nice results. The horror stories you may have heard only relate to people using 'compound' hennas, again, like you would buy in the store, mixed with other ingredients.
How it basically works: Henna can be combined with an acid (lemon juice, apple cider vinegar) and left to sit for 12 hours to release the dye. It can then be added to color the hair (usually for 2 hours) or it can be diluted and/or applied for a lesser duration, to add just a touch of tint and gloss to the hair. Indigo can be mixed with water and mixed into the Henna, or applied seperately after a Henna treatment. Cassia can be applied alone, or added to the aforementioned mixes. These plants should be purchased in a pure form (not in mixes from the beauty supply).
Where you can find out more: You can find a wealth of information at this website: www.hennaforhair.com about how to color your hair with these plants, and a very interesting history. There are also personal mixes, techniques, forums where you can ask questions about your specific hair type/goals, and order the products. You can also order small samples very inexpensively so that you can experiment on 'brush harvested' hair. I can't say enough great things about the women who run this website. If you are curious, and check it out, they offer all the info and help you need to become confident about trying this.
I have also since read on many natural health and hair sites that Honey can be used as a natural lightener. So if you are a blonde, perhaps that will work for you, as well as lemon juice. One could also use the cassia to get the brilliant shine that henna gives, without turning into a redhead! If I ever grow my natural hair out again, this is what I will do!
One last thing I want to say, is that it feels very good to get off of the chemical-dye train, to find natural plant dyes that achieve colors and results so beauteous that nature could only provide. It may seem time-consuming at first, but after learning and becoming experienced with the use of these dyes (and it doesn't take long!) it has become a nice beauty ritual; it feels more natural and personal...and has become something I look forward to doing, taking time to relax while the mix does it's magic, and the hair is always more beautiful each time! It has been about 2 years that I have been using these plant dyes, and I am glad to be able to share this info on earth clinic, so that perhaps others can start using this too.