256 RGB Colours – Red to Yellow



256 RGB Colours - Red to Yellow

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.
No! The colours produced by mixing primary colours are not spectral colours. Spectral colours are produced by a single wavelength of light.
Yes! The primary colours red, green and blue are used to produce secondary colours when using the RGB and HSB colour models.
Secondary colours are the colours produced by mixing pairs of primary colours in equal proportions. The secondary colours in the RGB colour model are cyan, magenta and yellow.

About the diagram

This is one of a series of six diagrams that together show all 1530 fully saturated colours in the RGB colour model.

Each diagram shows 256 colours starting with a primary and finishing with a secondary colour or visa-versa:

  • Red (primary colour) to yellow (secondary colour)
  • Yellow (secondary) to green (primary)
  • Green (primary) to cyan (secondary)
  • Cyan (secondary) to blue (primary)
  • Blue (primary) to magenta (secondary)
  • Magenta (secondary) to red (primary)

Understanding the diagram

  • All the colours in this diagram have been produced by mixing different proportion of red and green light.  The third primary colour, blue, is always off.
  • The diagram shows a stripe of red (primary colour) at the top, so, red has been turned to maximum and green to minimum intensity.
  • The stripe of yellow at the bottom results from both red and green being set to maximum intensity to produce the secondary colour.
  • The block of colour swatches between the stripes are made up of 16 rows and 16 columns.
  • The first swatch at top left matches the red stripe: red = 255, 00, 00.
  • The last swatch at bottom right matches the yellow stripe: yellow = 255, 255, 00.
  • To make sense of this, it helps to understand how RGB colour notation works:
  • When mixing any RGB colour, three numbers (separated by commas) show how much red, green and blue light is to be used.
  • 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

RGB colour values

Now let’s look at RGB colour values in detail

RGB colour values are represented by decimal triplets (base 10) or hexadecimal triplets (base 16). These triplets 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.
  • Decimal numbers between 0 and 255 are selected for each value:
  • Red = 255, 00, 00
  • Yellow = 255, 255, 00
  • 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.
  • Hexadecimal numbers between 00 and FF are 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 are: 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 are: 10,11,12,13,14,15,16,17,18,19,1A,1B,1C,1D,1E and 1F.

Some key terms

RGB colour

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

Additive colour

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

What is the trichromatic colour model?

The trichromatic colour model is a theory of colour that establishes terms, rules and methods to enable human colour vision ...


Things appear coloured to an observer because colour corresponds with a property of light that is visible to the human ...

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