This is what you really see when you close your eyes

When you close your eyes in total darkness, the color you see isn't black, but a dark shade of gray sometimes called eigengrau. 

The term's origin is German, and it translates approximately to "significant gray" as eigen means "one's own" and "grau" means "gray."

Why do we see this gray shade and not black? 

When our brains process visual information, contrast is more important than absolute brightness. Darkness as we see it is relative to the brightest thing we're looking at. 

For example, the night sky appears darker than eigengrau due to the contrast of the stars.

In the studies

In research studies, you're unlikely to see the word eigengrau pop up, as scientists prefer to use technical terms like visual noise or matching background. No matter which term is used, they all relate to how our eyes react to light and adapt to darkness.

The perception of color is considered a phenomenon created by the retina or its neural connections with the brain. Yet the gray color isn't completely stable. 

As time passes and we keep our eyes closed when we sleep, for example, the gray seems to gradually lighten or even appear to have touches of color in it.