The RGB colour cube

The RGB colour cube draws every colour a screen can show as a point inside a cube. Its three edges measure the screen's three lights, red, green and blue. Black sits in one corner and white in the opposite one.¹

Three lights, three axes

Each pixel on a screen is made of three small lights. RGB is an additive colour model: light is added to light, so the more of each, the brighter the result.¹ If each light gets a value from nothing to full, any colour the pixel can show is three numbers, and three numbers are a position in space. Put red on one axis, green on the second and blue on the third, and all the possible colours fill a cube.

The corner where all three values are zero is black; the opposite corner, all three at full, is white.¹ The diagonal between them runs through the greys, where the three values are equal. Three corners hold red, green and blue on their own. The last three hold two full lights each: yellow, cyan and magenta, each the complement of the light that is missing (cyan of red, magenta of green, yellow of blue).¹

16,777,216 colours

Modern systems usually store each of the three values in 8 bits, giving 256 levels, from 0 to 255.¹ The cube then has 256 steps along each edge and 256 × 256 × 256 = 16,777,216 points: the "16.7 million colours" of a screen with 24 bits per pixel.¹

New drawing

The same cube in ink

Print works the other way round. Ink takes light away from white paper, so a printed colour cube is built from the complements, cyan, magenta and yellow, with unprinted paper in the corner where no ink is used.^1, 2

In Lund in the 1970s, the mathematician Mikael Jern wrote software for Lund University's ink-jet colour plotter, built by Hellmuth Hertz, that drew such a cube: 17 × 17 × 17 small cubes.^3, 4 The plotter printed three inks on top of each other, and Jern made lighter and darker tones with a matrix of 4 × 4 dots.⁴ His cube had 4,913 colours where a screen's has more than sixteen million. How it was made, and who later signed it, is told in JAEV's editorial The colour cubes and in the notes on the colour plotter and Jern's COLOR program.

Where to see it

Olof Broström's Automatic Colour Cubes, 122 works made one a day on JAEV's server from 10 October 2026, starts from Jern's ink cube rather than the screen's. Each work reduces the cube to its outer shell and opens it along the edges that one of Sol LeWitt's Incomplete Open Cubes leaves out, so the inside of the colour range becomes visible. The works exist as print files in the three inks plus black; the images on the exhibition page are, in its words, "translations for the screen".²