At eHow you can find a lot of instructions on how to extract dyes from plants or parts of plants and so forth.
One instruction is e.g. ‘How to Extract Dye From Leaves and Grass’.
I tried some of them with different results, some worked better then others.
But unfortunately I didn’t record what I did, so if I needed some dye today I had to start from scratch.
That way everything stays interesting for me ;-)))
Links:
eHow: A website with how-tos galore
How to Extract Dye From Leaves and Grass
Search results for ‘extract dye’ at eHow