How to run it

1. Sit at arm’s length from the screen in a dim room. The darker the room, the stronger the after-image.
2. While the colour is up, rest the eyes on the small dot at its centre and keep them still. Blink normally, but do not let the gaze wander — a moving eye smears the after-image.
3. When the tone sounds, close the eyes and keep them closed. The colour will reappear on the inside of the eyelids.
4. Hold it on the mind screen. When it fades, rebuild it from memory rather than opening the eyes.
5. A second tone tells you to open the eyes for the next colour. Three tones together mean the practice is finished.

The after-image usually arrives in the opposite colour — red returns as blue-green, yellow as violet, green as pink. That is the eye recovering, and it is the sign the gazing worked. With practice the involuntary flash gives way to an image you are holding deliberately, in the original colour. Both are useful; the second is the actual training.

Stop if the eyes ache or the head hurts. Reduce to 15 or 20 seconds of gazing rather than pushing through. Skip this practice altogether with epilepsy or any light-sensitive condition, and keep children to 15 seconds a colour with an adult in the room.