To observe colour changes lightly bruise the pileus and stipe surface by pressing and rubbing a finger to the surface, and cut a fruit-body in half longitudinally, to expose the context of the pileus and stipe. Bruising of the stipe base context can be necessary to accentuate colour changes. Colour changes may occur on the pileus or stipe surface or on the exposed sections of the context. Changes may be seen immediately or within a few minutes, and may fade rapidly. Colour changes often occur through normal handling of fruit-bodies.

Choose this state if: a yellow colour change occurs on cutting or bruising.

For example, a strong yellow stain is shown by Agaricus xanthodermus.