# RGB Colour Wheel with 3 Colours

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## Description

To find out more about the diagram above . . . . read on!

#### RGB Colour Wheel with 3 Colours

Look carefully at the diagram at the top of the page. Now check out the following questions (and answers)!

1. What is a RGB colour wheel?
2. What are the three primary colours when starting an RGB colourwheel?
3. What are the three secondary colours when building an RGB colourwheel?
4. Are equal proportions of primary colours used to produce secondary colours?
5. Can all the colours in a colourwheel be produced by mixing pairs of primary colours in different proportions?

Introducing the diagram! Read back and forward between the image at the top of the page and the explanation below!

This is one of a series of diagrams exploring RGB colour wheels. Colour wheels demonstrate or simulate the affect of colour mixing.

Colour wheels can be used to explore the effect of mixing any type of colour. Light, inks, dyes, artist’s paints, pigments and colourants all produce other colours when mixed together.

Whilst a colour model outlines a method for mixing and using different types of colour, a colour wheel explores what happens in practice.

Understanding the diagram

• A colour wheel fills the centre of the diagram and in this case has three segments showing the RGB primary colours.
• The RGB codes corresponding with each colour appear to the left of the wheel.
• Notice how the colour notation works:
• Three numbers (separated by commas) show how much red, green and blue light is used to produce each colour.
• The minimum value for each light source is 0. In this case the light is fully off.
• The maximum value for each light source is 255. In this case the light source is fully on.
• As each number increases so does the intensity of the corresponding light but the wavelength and so the colour we see stays the same.
 RGB colour values Light source Red Green Blue Maximum value for each light source (fully on) 255 , 255 , 255 Values between 0 and 255 1 to 254 1 to 254 1 to 254 Minimum value for each light source (fully off) 0 , 0 , 0

What is an RGB colour wheel

• The purpose of an RGB colour wheel is to demonstrate or simulate the effect of projecting coloured lights, corresponding with the additive primaries (red, green and blue), onto a dark surface.
• In laboratory conditions, light sources are of equal intensity when fully on but can be turned down in 256 equal steps till fully off. The wavelengths of the light they output are set to values such as:
• Red = 625 nanometres
• Green = 500 nanometres
• Blue = 440 nanometres
• When coloured lights are projected and focused onto a surface they form overlapping circles. Colour wheels however are usually divided into segments like the spokes of a wheel on a bicycle.
• For everyday purposes, the most straight forward way to explore the RGB colour model is on a computer using software that allows different RGB colours to be selected.
• RGB colour wheels have a minimum of three segments. These are filled with the red, green and blue additive primary colours.
• When exploring RGB colour wheels the first thing to establish is what happens where pairs of primary colours of equal intensities overlap.
• Where red and green light sources overlap they produce yellow.
• Where green and blue light sources overlap they produce cyan.
• Where blue and a red light sources overlap they produce magenta.
• Yellow, cyan and magenta are called secondary colours and fill the segments between the primary colours on a colour wheel with six segments.
• Mixtures of equal intensities of pairs of secondary colours are called tertiary colours on a colour wheel with twelve segments.
• Additional colours are produced by continuing to overlap equal intensities of adjacent pairs of colours.
• The range of colours that can be produced on a computer screen by an RGB colour wheel is limited only by the system of notation, the resolution of the device they are displayed on and by the ability of an observer to distinguish between similar colours.

RGB colours are produced:

• On a computer or mobile phone screen by juxtaposing tiny dots of light corresponding with the three primary colours, red, green and blue.
• In computer software and apps by selecting RGB colours using swatches or by selecting RGB colour values (codes) using decimal or hexadecimal notation.

Look at a computer screen or TV using a magnifying glass to see the three RGB primary colours. Then step back to see how different colours appear when all the pixels merge together.

RGB and spectral colour

RGB colour values

RGB colour values are represented by decimal triplets (base 10) or hexadecimal triplets (base 16). These are used in software and apps to select a colour.

In decimal notation, an RGB triplet is used to represent the values of red, then green, then blue.

A range of decimal numbers from 0 to 255 can be selected for each value:

• Red = 255, 00, 00
• Yellow = 255, 255, 0
• Green = 00, 255, 00
• Cyan = 00, 255, 255
• Blue = 00, 00, 255
• Magenta = 255, 00, 255

In hexadecimal notation an RGB triplet is used to represent the value of red, then green, then blue. A range of hexadecimal numbers from 00 to FF can be selected for each value.

The hash symbol (#) is used to indicate hex notation:

• Red = #FF0000
• Yellow = #FFFF00
• Green = #00FF00
• Cyan = 00FFFF
• Blue = #0000FF
• Magenta = #FF00FF

The sequence of hexadecimal values between 1 and 16 = 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E and F.

The sequence of hexadecimal values between 17 and 32 = 10,11,12,13,14,15,16,17,18,19,1A,1B,1C,1D,1E and 1F.

• RGB colour is an additive colour model that combines wavelengths of light corresponding with the red, green and blue primary colours to produce other colours.
• RGB colour is called a model because it is a method that can be followed to produce any colour from a combination of red, green and blue light sources.
• Red, green and blue are called additive primary colours in an RGB colour model because they can be added together to produce other colours.
• When mixing light, each RGB primary colour is called a component of the resulting colour.
• Different colours are produced by varying the intensity of the component colours between fully off and fully on.
• When the light sources that produce the red, green and blue primary colours are at full intensity, together they produce white.
• Each light source at full intensity produces a fully saturated colour.
• When any two fully saturated RGB primaries are combined they produce a secondary colour (yellow, cyan or magenta).
• Some applications of the RGB colour model can produce over 16 million colours by varying the intensity of each of the three component primary colours.
• The additive RGB colour model cannot be used for mixing opaque pigments, paints or powders. To understand these colourants find out about subtractive colour models.
• The RGB colour model does not define precise wavelengths (or band of wavelengths) for the three primary colours.
• When the exact composition of primary colours are defined, the colour model then describes an absolute colour space.

Follow the blue links for definitions . . . . or check the summaries of key terms below!

#### Some Key Terms

Move to the next level! Check out the following terms.

Additive colour is a method of mixing different wavelengths of light to produce other colours. An additive approach to colour ...

#### Colour wheel

A colour wheel is a diagram based on a circle divided into segments. The minimum number of segments is three ...

#### Primary colour

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

#### RGB colour

To be clear about RGB colour it is useful to remember first that: The visible spectrum is the range of ...

#### RGB colour values

RGB colour values are expressed as decimal triplets or hexadecimal triplets and are used in software applications to select specific ...

#### ROYGBV

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

#### Secondary colour

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 ...

#### Colour model

A colour model is a mathematical system used to describe colours using a set of numeric values. A colour model ...

#### Slides

All images on the lightcolourvision.org website are available for download as either slides or diagrams.

All slides share common specifications:

• Titles: All slides have titles.
• Backgrounds: Black, framed with a violet gradient.
• Size: 1686 x 1124 pixels (3:2 aspect ratio).
• Slides are available in two file formats: JPG, AI (Adobe Illustrator).

Slides are optimized for viewing on-screen or with a projector.
Diagrams are optimized for printing on A4 pages in portrait format.

#### Diagrams

All images on the lightcolourvision.org website are available for download as either slides or diagrams.

All diagrams share common specifications:

• Titles: No titles.
• Backgrounds: White.
• Size: 1686 pixels wide. So all diagrams reproduce at the same scale when inserted into Word documents etc.
• Labels: Calibri 24pt Italic.
• Diagrams are available in two file formats: JPG, AI (Adobe Illustrator).

Diagrams are optimized for printing on A4 pages in portrait format.
Slides are optimized for viewing on-screen or using a projector.

#### JPG file format

• Text on JPG images with white backgrounds is styled as Calibri 24pt Italic.
• If the image you need is not exactly right, download it as an AI (Adobe Illustrator) file and edit it.
• All the images on these Resource Pages were created in Adobe Illustrator and are vector drawings.

Did you know:

• JPG stands for Joint Photographic Experts Group who created the standard.
• The JPG file extension is used interchangeably with JPEG.
• JPG files can be compressed for use on websites.
• JPG files can be placed or pasted directly into MS Office documents.

#### AI (Adobe Illustrator) file format

• All AI images available for download from lightcolourvision.org are 1686px wide.
• All the images on these Resource Pages were created in Adobe Illustrator and are vector drawings.
• Vector drawing can be scaled up or down without any loss of quality.

Did you know:

• Adobe Illustrator can save or export AI files to other formats including PDF (.pdf), PNG (.png), JPG (.jpeg) and SVG(.svg) etc.