Spectrum

hold, and stare at the dot. your eye paints the rest.

stare at a picture in opposite colours; on white your tired eye paints it back, and makes magenta, the colour with no wavelength

Stare at one colour and the cones that catch it tire. White lights every kind of cone, and the tired ones answer weakly, so for a few seconds you see the opposite colour where the picture was. Green leaves magenta, which no single wavelength makes: the brain builds it from red and blue light with no green. The colours are faint and fade; they are your eye, not the screen.

no wavelength is magenta. it is red plus blue with no green, which is what a green-tired eye sees in white.

Concepts: color, perception.

An interactive you play with one thumb, on Wundr.