The image above, when viewed at full size, contains one million pixels (a thousand by a thousand) and each one is a slightly different colour.
Each pixel in the display of your computer or phone contains three tiny lights: one red, one blue and one green. The display sets the apparent colour of a pixel by adjusting the intensities of those three lights – they are so small and close together that your eyes mix the three back into a single colour in your vision.
Inside the computer, a colour is represented by three numbers, representing the intensities of each of the red, green and blue lights on a scale from 0 to 256. (This is known as an RGB scheme for describing colours, often as distinct from the CMYK scheme – for cyan, magenta, yellow and black – that is used in printing.)
In the image above, the pixels methodically step through the gamut of RGB colours. The top left pixel is black – all colours set to zero – and the bottom right is white – all colours set to the maximum. In between, each small square works through the range of red and green values while the intensity of blue increases from square to square.
Originally published by Cosmos as One million colours
Cosmos
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