Chimerical colours

Chimerical colours are colours you can't normally see — they sit outside the range your eyes can ordinarily report.

How it works: staring at a strong colour fatigues the colour-sensing cells in your eye. Look away and they over-correct, leaving a ghost in the opposite colour — an afterimage. Land that ghost on the right background and the two mix into a colour that is normally impossible.

Stygian bluea blue as dark as black Stygian reda red as dark as black Self-luminous reda red that seems to glow Self-luminous greena green that seems to glow Hyperbolic orangeoranger than any real orange Hyperbolic greengreener than any real green

Press start, then keep your eyes fixed on the dot for 30 seconds. When the screen changes, keep looking at the dot — the impossible colour appears there. Blink gently if it fades.

Start