Mushrooms as a dying agent?

I've recently gotten into mushroom foraging.  It's quite easy to notice the immense variety of fungi..  they come in all sorts of shapes, forms, and colors.  The easiest mushrooms to find are often those with bright and vivid colors

Are mushrooms ever used for dying?
If so, are they effective?

Yes, mushrooms/fungi are used for dyeing...I've never tried them, but run across information as I'm interested in natural dyes of all sorts.
Here's a link to some basics http://mycopigments.com/

"Mordants offer a wide range of color from the Dyer’s Polypore"

I don't think the color of the mushroom necessarily indicates the dye color produced though and I would still want to know their toxicity and not use anything unidentified and possibly toxic if I were going to be processing them.  I've just recently been reading up on lichens as dye materials...such brilliant colors from some of them.