Closed-eye hallucinations are called phosphenes

Looking down at the shower drain, chin against my chest, waiting to dry, I aimed the drops falling from my forehead at the holes in the drain cover.

When I closed my eyes, an image of the drain cover remained, but the colors were inverted—the cover became dark like the holes and the holes became light like the cover.

After a few seconds, the hallucination faded. I opened my eyes and adjusted my head to get back on target.