# Using The RGB Colour Model

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This diagram explores the RGB colour model. It looks at how wavelengths of light corresponding with the RGB primary colours are combined to produce secondary colours.

What you need to remember:

• Mixing different wavelengths of light to produce other colours, is called an additive colour model or an additive approach to colour.
• Red, green and blue (RGB) are additive primary colours. This means that when these wavelengths of light are projected onto a dark surface they combined to produce other colours.
• If wavelengths of light corresponding with all three additive primary colours are projected in equal amounts onto a dark surface the result is white.
• If wavelengths of light corresponding with all three additive primary colours are projected in unequal amounts onto a dark surface many thousands of colours can be produced.
• Secondary colours are the colours produced when pairs of primary colours are combined in equal or unequal proportions.
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## Description

#### Using The RGB Colour Model

###### TRY SOME QUICK QUESTIONS AND ANSWERS TO GET STARTED
_x000D_ _x000D_ Red, green and blue are the three primary colours in the RGB colour model.
RGB is a colour model used to produce a full palette of colours by mixing red, green and blue light sources in different proportions.
RGB refers to the colours red, green and blue. These are the primary colours used by the RGB colour model to mix wavelengths of light to produce a palette of as many as 16 million colours.

• This diagram explores the RGB colour model. It looks at how wavelengths of light corresponding with the RGB primary colours are combined to produce secondary colours.
###### What you need to remember
• Mixing different wavelengths of light to produce other colours, is called an additive colour model or an additive approach to colour.
• Red, green and blue (RGB) are additive primary colours. This means that when these wavelengths of light are projected onto a dark surface they combine to produce other colours. The colour produced depends on the intensity of each light source.
• If wavelengths of light corresponding with all three additive primary colours are projected in equal amounts onto a dark surface the result is white.
• If wavelengths of light corresponding with all three additive primary colours are projected in unequal amounts onto a dark surface many thousands (or millions) of colours can be produced.
• Secondary colours are the colours produced when pairs of primary colours are combined in equal or unequal proportions.
###### Understanding the diagram
• Three circles of light are projected onto a dark surface in the top half of the diagram. These are the additive primary colours – red, green and blue.
• Where the primary colours overlap they produce the secondary colours – yellow, magenta and cyan.
• Where all three primary colours overlap they produce white.
• The bottom of the diagram shows which primary colours are mixed in pairs to produce each secondary colour. and which secondary colours produce each primary colour.

#### Some key terms

A colour model is the how-to part of colour theory. Together they establish terms and definitions, rules or conventions and a system of notation for encoding colours and their relationships with one another.

A colour model is a way of:

• Making sense of the colours we see around us in the world.
• Understanding the relationship of colours to one another.
• Understanding how to mix each type of coloured media to produce predictable results.
• Specifying colours using names, codes, notation, equations etc.
• Organising and using colours for different purposes.
• Using colours in predictable and repeatable ways.
• Working out systems and rules for mixing and using different types of colour.
• Creating colour palettes, gamuts and colour guides.
• To be clear about the RGB colour model it is useful to remember first that:
• The visible spectrum is the range of wavelengths of the electromagnetic spectrum that correspond with all the different colours we see in the world.
• A spectral colour is a colour corresponding with a single wavelength of visible light, or with a narrow band of adjacent wavelengths.
• The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet. However, because of the way the eye works, we can see many other colours which are produced by mixing colours from different areas of the spectrum. A particularly useful range of colours is produced by mixing red, green and blue light.
• RGB colour is an entirely different approach to producing and managing colour.
• RGB colour is an additive colour model in which red, green and blue light is combined in various proportions to reproduce a wide range of other colours. The name of the model comes from the initials of the three additive primary colours, red, green, and blue.
• Except for the three primary colours, RGB colours are not spectral colours because they are produced by combining colours from different areas of the visible spectrum.
• RGB colour provides the basis for a wide range of technologies used to reproduce digital colour.
• RGB colour provides the basis for reproducing colour in ways that are well aligned with human perception.
• When an observer has separate controls allowing them to adjust the intensity of overlapping red, green and blue coloured lights they are able to create a match for a very extensive range of colours.
• When looking at any modern display device such as a computer screen, mobile phone or projector we are looking at RGB colour.
• Magenta is an RGB colour for which there is no equivalent spectral colour.
• An additive colour model explains how different coloured lights (such as LEDs or beams of light) are mixed to produce other colours.
• Additive colour refers to the methods used and effects produced by combining or mixing different wavelengths of light.
• The RGB colour model and HSB colour model are examples of additive colour models.
• Additive colour models such as the RGB colour model and HSB colour model can produce vast ranges of colours by combining red, green, and blue lights in varying proportions.
• An additive approach to colour is used to achieve precise control over the appearance of colours on digital screens of TVs, computers, and phones.

Primary colours are a set of colours from which others can be produced by mixing (pigments, dyes etc.) or overlapping (coloured lights).

• The human eye, and so human perception, is tuned to the visible spectrum and so to spectral colours between red and violet. It is the sensitivity of the eye to the electromagnetic spectrum that results in the perception of colour.
• A set of primary colours is a set of pigmented media or coloured lights that can be combined in varying amounts to produce a wide range of colour.
• This process of combining colours to produce other colours is used in applications intended to cause a human observer to experience a particular range of colours when represented by electronic displays and colour printing.
• Additive and subtractive models have been developed that predict how wavelengths of visible light, pigments and media interact.
• RGB colour is a technology used to reproduce colour in ways that match human perception.
• The primary colours used in colour-spaces such as CIELAB, NCS, Adobe RGB (1998) and sRGB are the result of an extensive investigation of the relationship between visible light and human colour vision.

ROYGBV is an acronym for the sequence of hues (colours) commonly described as making up a rainbow: red, orange, yellow, green, blue, and violet.

• A rainbow spans the continuous range of spectral colours that make up the visible spectrum.
• The human eye is tuned to the visible spectrum and so to spectral colours between red and violet.
• ROYGBV are colours associated with a range of wavelengths rather than with unique values.
• The visible spectrum is the small band of wavelengths within the electromagnetic spectrum that corresponds with all the different colours we see in the world.
• The fact that we see the distinct bands of colour in a rainbow is an artefact of human colour vision.

A secondary colour is a colour made by mixing two primary colours in a given colour space. The colour space may be produced by an additive colour model that involves mixing different wavelengths of light or by a subtractive colour model that involves mixing pigments or dyes.

• Secondary colours produced by an additive colour model are quite different from the spectral colours seen in a rainbow.
• A spectral colour is produced by a single wavelength, or a narrow band of wavelengths, within the visible spectrum.
• A secondary colour produced by an additive colour model results from superimposing wavelengths of light from different areas of the visible spectrum.
• For the human eye, the best additive primary colours of light are red, green, and blue.
• A colour model, underpinned by a colour theory, provides a precise and replicable approach to understanding:
• How the human eye perceives light and interprets colour.
• Different types of colour such as the colours produced when mixing lights, pigments or inks.
• How to manage the diverse ways colour is processed by equipment such as cameras, digital screens and printers.
• Whether or not we recognize it, whenever we are working with colour, we are adopting a colour theory, a colour model and a colour space.