All the books about chicken-raising recommend that a "dummy" egg (plastic, wooden, or stone) be placed in the laying boxes so that hens--who cannot be accused of intellectual brilliance by anyone who is paying attention--will lay their own eggs in a good location instead of, for example, under the wheel of the tractor.
None of the books about chicken-raising mention the ability to discern color, but it's pretty clear that, if our Minerva Louises have noticed that the fake eggs in their nest boxes are unusual, they probably attribute the bizarre colors to some other hen. They settle right down each morning on top of the yellow, pink, and orange plastic eggs and lay their own eggs in the same little nest.
In some cases, they settle right down and apparently break open the little seam on the side of the plastic egg:
I have found two eggs like this. What the....???
The first time, I thought maybe Jim or Willy had put an egg inside the plastic to play a joke on me. The second time, the guys were in plain sight when I checked the nest boxes, and the egg was still warm--and the hen was still sitting on it!
Then, there was the incident this morning.
I had just turned the horses out into the pasture and heard an "announcement" cackle, so I walked over to check the chickens. There were, in fact, THREE hens in nest boxes when I opened the little door. Two of them were sitting on eggs.
When I reached under the third lady, she stood up and laid an egg into my hand.