Yellow staining agarics are quite common: these pictures are from several different locations which I passed while strolling around Wolverhampton in the first half of the month. They could easily be confused with common field mushrooms, the wild form of ordinary supermarket mushrooms.
But these aren’t good to eat, guaranteeing an upset stomach. The giveaway is the yellow staining – a discolouration of the damaged flesh when the mushrooms are bruised or broken.