Night Vision

The first practical night vision devices were developed in Germany in the mid-1930s. Night vision goggles are usually green, because people can see more shades of green than other colors. Because the eye is most sensitive to light wavelengths nearer green, the display can be a little dimmer, which conserves battery power.

Photons that hit the lens at the front of night vision goggles are carrying light of all colors, but when they are converted to electrons, there is no way to preserve that information. Effectively, the incoming, colored light is turned into black and white. It is also easier to look at green screens for long periods than to look at black and white ones. That is also why early computer screens were mostly green.