I'm into mushrooming, I have pics to prove it but then I should bother to find them and I can't properly photoshop them and although Corel PhotoPaint works just fine, not my current screen. And back then, I wasn't in the mood.
I however kept various stuff. Because, the internets say that one can extract dye from mushrooms. I read a bit here and a bit there but they were not particularly useful because good part of the descriptions started with something like Navajos used the Dyer's Mushroom... and since there's no proper name given, I have no clue if this species grows around here. (1) One of the more interesting reports said that fermentation helps release the pigments. The others said that about salt, ammonia and a few other substances. One of the recipes called for wool and mushrooms immersed in a jar and left to ferment for a few months in full sun, that it's fine, the stench will go away after a few months.
This has somehow caught my attention although my fermentation experiments went only as far as getting some kefir grains and feasting on sour milk until the culture turned bad. I hear, however, that the wild bacteria that are just around here could work pretty well, too. I got a mixture of bolete leftovers (good stuff gets eaten or conserved by drying), some dried Laccaria amethystina - they say that it turns your food purple but when dried, it lost a bit of colour so I wasn't very sure - and orange mix of Hydnum repandum and chanterelles.
I needed to go away for a while so I left the mushrooms sit in their respective vessels for two days.
Bowl: chanterelle and hydnum mix; jar: Laccaria; beer glass: bolete mix.
The soaked mushrooms did develop some character that included bubbles and a bit of suspicious smell. The Laccaria jar was a fail, no apparent dye - or at least I didn't trust the greenish colour enough so to compost it went.
The usual method of boil stuff - soak yarn - keep warm for a few hours should do the trick in theory. There should be some Finis coronat opus bit - beautifully dyed samples or some such. However, it didn't work at all. Alum mordant or not, the dye just didn't set. Not at all.
There is a contest in photography of all things fermented. Should you want, gimme a thumbs up - I want to outrun at least one of the wonderful pickles, alcoholic beverages and whatnot.
(1) which is the scientific name in Latin. The only thing that works all over the place. Well, mostly, and still better than common names, much better.