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Colours on a screen — Computing, 4–6

A screen makes colours with tiny lights. Red, green and blue lights can combine to make many colours.

Three lights make many colours

A screen has tiny spots of red, green and blue light. They are so small that your eyes see their combined light as one colour. Change how bright each light is and the screen can show yellow, purple, white and many other colours.

Why screens use light

Paint mixes by taking light away, but a screen must make light reach your eyes. Using three kinds of light gives each tiny spot a simple way to make many colours. This lets one screen show a photo, a game or a film without needing a different screen for every colour.

Making yellow

Look at one yellow patch on a screen. Its red light is bright, its green light is bright, and its blue light is off or very dim. Your eyes receive red and green light together and see yellow. The tiny lights are not yellow paint.

Screen mixing is not paint mixing

You may expect red and green screen lights to make brown, because red and green paint often make a dark colour. That expectation makes sense from painting. A screen adds light instead: red and green together look yellow, while adding all three brightly makes white.

Pictures, games and signs

The same tiny red, green and blue lights make the colours in a cartoon, a map, a game and a video call. A designer chooses how bright each kind should be at every spot. When you change a screen’s colour settings, you are changing those light mixtures.

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