Colour model

A colour model is the how-to part of colour theory in so far as a colour theory is a system built upon a correspondence between ideas and the real world and a colour model is a method of putting those ideas into practice.

A colour model derived from a colour theory enables an exact and reproducible approach to colour.

  • A colour theory and related colour model can be used to establish terms and definitions, rules or conventions and systems of notation for encoding colours and managing their relationship with one another.
  • Whether or not we recognise it, whenever we are working with colour, we are adopting a colour theory, a colour model and a colour space.
  • The most practical colour models are built into applications such as Adobe Creative Cloud and enable accurate output of colour information to TVs, computers and phones or printing onto paper and other surfaces.
  • Widely used colour models include:

A colour model derived from a colour theory is a way to:

  • Use colours in logical, predictable and repeatable ways.
  • Make sense of colour in relation to human vision, to what we see around us, as we work at a computer screen or prepare to produce a printed image.
  • Understand how to mix a particular colour from light or pigments, inks and dyes to produce predictable results.
  • Specify colours using names, codes, notation, equations etc.
  • Organise and use colour for different purposes and in different contexts (fabrics, interiors, vehicles).
Why use colour models?
  • Colour models help to relate colours to:
    • One another
    • Light sources, objects and materials
    • Perceptions and experiences.
  • Colour models make sense of the fact that coloured lights, transparent inks and opaque paints (etc.) all produce different results when mixed.
  • Colour models help us manage the fact that colours mean and feel different and have different associations depending on context.
  • Colours models help us manage the fact that colours behave and appear differently:
    • When emitted by different types of light source.
    • When applied to, mixed with, or projected onto different materials.
    • When used for different purposes (fabrics, electrical wiring and components, print media, movies etc.)
    • When seen or used in different situations (indoors, in sunlight, in low light, on a digital display etc.)
About additive and subtractive colour models

There are two principal types of colour models, additive and subtractive.

About colour models, colour spaces and colour systems
  • A colour model is usually device-dependent. This means that the exact colour produced by a model depends on the device that reproduces it not on the colour model itself. So a colour specified as R=220, G=180, B=140 might appear differently on two digital monitors or when printed by different printers with the same specifications.
  • A colour space determines the range of colours available within a specific workflow and may be determined by a user or programmatically. Colour spaces can be very limited when the plan is to print a photo on a low-price digital printer, large when the same image is viewed on a high-definition digital display, or huge when the original scene is viewed in bright sunlight on a summer day.
  • A colour management system considers all the factors that affect how the colours in an image are dealt with from start to finish. Factors include how an image is captured, how information is encoded, how it is edited, how it will be viewed and decisions about final reproduction.
Spectral colour model

The spectral colour model is an additive colour associated with rainbows and the refraction and dispersion of wavelengths of light into bands of colour.

RGB colour model

RGB (red, green, blue) is an additive colour model based on the trichromatic theory of colour vision. It is widely used in video cameras, for producing colour on digital screens and with software such as Adobe Creative Cloud.

CMY(K) colour model

CMY (cyan, magenta, yellow) is a subtractive colour model. It is the standard colour model for digital printing. Printers include a fourth component, black ink (K), to increase the density of darker colours and blacks.

RYB colour model

RYB (red, yellow, blue) is a subtractive colour model. It is the standard colour model used for artist paints and when mixing inks, dyes and pigments.

HSB colour model

HSB (hue, saturation, brightness) is a popular additive colour model. Many people find it more intuitive and so easier to use than RGB, particularly when adjusting colour using digital applications such as Adobe Creative Cloud.
HSB is one of a family that also includes HSV (hue, saturation, value) and HSI (hue, saturation, intensity).