Long ago, in the days of black and white photography, I did some film developing. In my dark room I needed a very low light level. Years before I had acquired a neon bulb that screwed into a regular medium socket. I used it in the ceiling socket.

The Neon bulb produced a dim orange light. The neon was contaminated with a small amount of argon, which is strong in violet, but so little argon I could barely detect the violet. The odd thing is, with this light I could see full color at a ligh level so low I could normally see no color.