Thinking about the green ball mystery, I took some photos of the ball pit this morning before sunrise.

This was a half-hour before sunrise, so the scene is lit by the red LEDs in the solarium. 

Human eyes can perceive red, green and blue light.  Any color we see is a mix of those three.  Dogs don’t perceive red light as well.  For this reason, the solarium is lit with red LEDs to give me a competitive edge over Sparky.

Natural white light is composed of all wavelengths of light in the visible spectrum.  Conventionally, we call those the ‘colors of the rainbow’.  Those are red, orange, yellow, green, blue, indigo and violet, (ROYGBIV), but it’s a spectrum of light rather than specific colors.

For an object to look green, it has to be illuminated with green light.  White light has green in it, so that counts.  Otherwise, the object looks dark.

LED light is different than natural light because it contains specific colors of light, rather a spectrum.  Here is the snack pit illuminated by red LED light versus natural light.

Natural light was needed to take the second photo, so it was taken a couple of hours later.  The snack pit had been shifted a few inches, which I don’t recall doing, but most of the balls are in the same place in both photos. 

Turning on room lights to take the second photo would not be adequate because all of my lights are LEDs.  White light from an LED bulb is a mix of only a few colors of light.  Incandescent or halogen lights provide natural light with a broad spectrum.

Here are the balls in order of increasing light wavelengths.

Even before sunrise, there is a tiny bit of natural light, but the blue and green balls look much darker under red LED light.  This doesn’t explain why only green balls were on the floor, but it may be related.