The term "eigengrau" comes from German — "eigen" (own/intrinsic) + "grau" (grey) — and was introduced by German psychologist Gustav Theodor Fechner in the 19th century. It describes the uniform dark grey perceived in conditions of total darkness — not truly black because the visual system is never completely inactive.

The colour of consciousness itself. Eigengrau is what seeing looks like when there is nothing to see — the brain's visual background radiation. It reveals that vision is not a passive reception of light but an active construction. The visual system, left without external input, generates its own colour. Philosophically, eigengrau suggests that colour is not in the world but in the mind — that we carry our own darkness with us.

Eigengrau exists at the intersection of neuroscience, philosophy, and art. James Turrell's Ganzfeld installations — rooms of uniform, extremely bright or extremely dark light — investigate the perceptual states that arise when the visual system loses spatial reference points. In total dark, the visual cortex begins generating its own imagery (hypnagogic hallucinations), of which eigengrau is the most consistent element. The concept challenges the assumption that colour is a property of objects rather than a construction of consciousness.