Years ago, my husband and I saw a custom painted pickup truck that changed colors depending on the angle from which it was viewed. Looking at it from the front, the color appeared green. Looking at it from the back, the truck appeared purple. We were amazed by this color-shifting paint job.
But tonight I realized that this was not ground breaking new technology. God did it a long time ago with the heads of mallard ducks. As Davey swam back in forth in front of me this evening, I watched his head color change from green to purple and back to green, depending on how the sunlight shone on him.