Found this one in the woods behind my house. One of my favorite mushrooms to find even though there's not much to do with it, it's beautiful just to look at!
The blue "milk" contains latex, so don't handle if you're allergic. It's related to regular milk caps and looks identical aside from the brilliant color.
Something that you don't often see in field guides: it smells quite sweet in addition to the usual earthiness.
I will be returning it to the forest floor to drop its spores in hopes I keep finding them.
There was someone on the other site that made dyes from them, to color natural fibers.
If you find the link for the recipe, please share!
By trying to find one, I got the impression that indigo milkcaps (Lactarius indigo) are not widely used for coloring, at least this was my understanding from the iNaturalist forum. I also tried to find it in the Mushroom Color Atlas - Index, but no luck there.
I found what it was - r/theShroomCrocheteers - but the community was closed and set to private following the API debacle.
If memory serves, the result of the experiment was a faint grey pigment. So none of the rich blues the cap is famous for.
Thank you for your input, anyways! I had to ask, I really like links hahaha
I'm sorry I couldn't be of more help.