Parrot waxcaps are small mushrooms. At first, they have a green colour similar to the feathers of some parrot species, but this soon fades to yellow.
The larger mushroom here has almost completely turned yellow, the tiny one at its feet is still green.
https://www.flickr.com/photos/davea2007/10958379245
Last time I spotted parrot waxcaps it was a morning after a hard overnight frost.