Other ways to stain wood:

I've been looking into more tannins, and although ebonizing the wood with the steel wool and vinegar seems the most interesting to me, here are a few others i plan on trying our too:

Dark tea: Use about 10+ tea bags, and let soak in boiled water for 2-3 hours. Use the tea-stained water as a dye.

Liquid bleach: Using a rag, apply liquid bleach to the wood surface.

Fruit juice: Juices such as raspberry or grape, but colour may go brown.

Food colourings: Bright coloured food dyes.

Shoe polish: To create a very dark ebonized look

Red wine: To create a deep brown/maroon colour.

EBONIZING WOOD

How to?:

1) Place (real) steel wool in a plastic jar
2) Pour vinegar into the jar
3) Soak the steel wool (over a week for best results)
4) Strain the liquid, and use liquid to brush onto the wood.

The darker the wood used, the darker the finish. For example, a very dark wood could look almost black.

COLOUR LIST: 
What makes pigments?

Black: Charcoal, bone black 

White: Chalk, bone

Red: Berries, "dragons blood", Madder plant, Cinnabar,
 - Dragons blood is a red resin that comes from some palm plants. 

Blue: Indigo leaves, duck poo

Yellow: Yellow clay, berries, gold leaf

Green: Plants

Recently i've been looking more into the scientific side of dyes and tannins, as well as inorganic and organic pigments. Inorganic pigments are the crystals of metal oxides.
Here is what i've found out:

INORGANIC PIGMENTS:

Chromium oxide green:
Usually known as chrome green, this pigment can be found in lead chromite. In the past, it was used as enamel in porcelain, which then was used as a painting pigment.

http://www.naturalpigments.com/chromium-oxide-green-pigment.html

 Ultramarine blue:
Originally comes from the stone lapis lazuli, and originates from Afghanistan.




https://www.google.co.uk/search?q=Mixed+metal+oxide++pigment&newwindow=1&client=firefox-a&hs=m0J&rls=org.mozilla:en-US:official&channel=fflb&source=univ&tbm=shop&tbo=u&sa=X&ei=8XJiVPTHEbiAsQTH0IKADg&ved=0CCIQsxg&biw=1280&bih=564

Link above for ways to buy these pigments. A lot of them are on Etsy! These pigments do come in all sorts of colours, including pinks, purples, oranges, and yellow.