I also found another list of natural dyes - I haven't tried them yet.
Yellow - Wild apple bark, onion skin, buckwheat husks. campion, or
the flowers of dog's fennel.
Green - sunflower seeds, wild elder berries, dark red or black
hollyhocks, bush anemones, birch, and mosses.
Dark Yellow - Alder buds, hazel ot chestnut leaves, walnut and apple
leaves, or oak bark.
Black - Sunflower seed husks + sulphate iron, bark of alder, young
leaves of black maple.
From "Pysanka: Icon of the Universe"; Tkachuk, Mary, Marie Kishchuk,
and Alice Nicholaichuk; Ottawa: U.W.A.C and National Museum Canada, 1977.