There are more healthy ways of coloring your hair. The best product for you depends on what you want to accomplish.
In my experience, more natural products deposit color on your hair and work great for covering grey,but so much on drastically changing the overall color unless your hair is grey.
I've used a brand called Naturtint for many years that uses natural ingredients and is free of ammonia, resorcinol and parabens. It also has no odor and can give you a slight color change depending on the color of your hair and the color you use. The manufactuer usually provides a color chart to help guide you in your color choice.
If covering grey is your goal, you'll need make sure the product you use says "100 percent grey cover" to get the best results.
In my experience henna doesn't work so well on grey, but does make your hair shine and can give a slight color "change".
The only draw back is that since they're more natural, they don't last as long. If you use a regular shampoo, it fades even quicker. A conditioning cleanser works best to prolong the more natural hair colors.
You can check out this link and read about some different types and brands of more natural hair color http://www.swansonvitamins.com/q?kw=hair+color. Be sure to read the ingredient list to sure your comfortable with them all. Health food stores carry them as well.