My experiences have been with using kakishibu, a rust colored natural color from fermented juice of the unripened astringent persimmons from Japan, Indigo dyes from Japan & India and cochineal, a scale insect from which the crimson-colored dye carmine is derived. I have also experimented with yellow onion skins and walnut hulls.
Soon I hope to use more natural dyed fabrics in my hat creations. Below is a photo of some of my cochineal dyed wool. Will post more of the pics from Jay's exploration class soon.