I’d not heard of this colour before but here is the definition from wikipedia
Eigengrau (German: “intrinsic gray” / literally: “own grey”), also called Eigenlicht (“intrinsic light”), dark light, or brain gray, is a term for the uniform dark gray background that many people report seeing in the absence of light.
see more? Cee’s Fun Foto Challenge
Lots of things afloat in Venice Weekly Photo Challenge