Hej,
This is my first time picking field mushrooms. When I got home, I noticed a bit of a yellow stain at the base of one of the smaller ones (you can see it in the picture), and also a little bit on one of the other's caps.
However, none of these mushrooms smell like anything but mushrooms. I also cooked them (as an experiment for now), as I read that xanthodermus go a more intense yellow and give off a more intense iodine odour when cooked. But they look and smell great (they actually look a lot more yellow in that photo than in real life). I can't see any noticeable yellow or weird smell even after cooking. I did taste a very little bit of them (cooked) and they don't exactly taste like store-bought bisporus mushrooms. Similar, but more strongly flavoured. A bit earthy.
But the fact that there was clear yellow staining on at least one (small one, center in the photo of them all piled up) does concern me. Someone told me that other edible agaricus mushrooms can indeed stain a little bit yellow, just not much.
How safe am I do you think? Pictures say it all - found in Sweden in the autumn (fall) in cow meadows.