Tips for all natural hair dyes?

Henna = red

Indigo alone over henna = black

Henna and indigo = brown, tone depends on ratio of henna to indigo

Henna and indigo and amla = brown with cool tones rather than warm tones

Henna and a tiny amount of indigo = burgundy or auburn

Cassia = blonde, only shows up on lightest hair like light blonde or grey

Henna and cassia = honey, strawberry blonde

Buxus = alone is a grey color

Henna and buxus = ash browns

Henna, cassia, buxus = ash blondes and dishwater

Nothing else will really add much color. Nothing is permanent except indigo and henna, and they are very permanent. Henna makes other plants permanent, so henna/buxus doesn't wash out, but buxus alone would. Coffee doesn't stain for very long, and it will make you jittery. Occasionally you can "push" henna's red into one direction or another by using different juices rather than lemon. Blackberry juices makes a purple color, paprika might make it more fiery red, but all these changes are likely to be temporary, after a few washes it's a normal henna red.

http://www.hennaforhair.com/mixes/index.html

I've used henna and a semi permanent natural dye with henna in it. The henna doesn't seem to last too long, but it seemed really good for the hair. I have dark brown hair, going gray... It covered the gray for almost a month then washed out. It's nice not to use chemically based dyes. They are very toxic.