Primary colours. What they are and why they’re important.

Primary colours. What they are and why they’re important.

Giovanni Blandino Published on 9/1/2023

A brief guide to primary colours, secondary colours and colour theory.

Primary and secondary colours may be something taught at primary and secondary school, but it’s knowledge that’s often forgotten!

In fact, colour science and colour theory are very important: colours affect our psychology, so fully understanding how they work can help us in all sorts of fields. In graphics and design, for example, as well as in marketing: consumer choices can be influenced by colours!

Today, we’re giving you a refresher on the basics of colour theory: primary and secondary colours. And we’ll be busting a few myths along the way! For example: are the primary colours really red, yellow and blue? Yes, but it’s only partly true. Read on to find out why!

What are primary colours?

It is usually said that primary colours are the colours from which all others can be made, with the help of black and white . This is the definition of primary colours that we learnt at school.

Traditionally, the primary colours are said to be red, yellow and blue. These are the colours found in Itten’s famous colour wheel: the central triangle depicts the primary colours, the three triangles surrounding the central triangle show the secondary colours and the outer circle the tertiary colours.

 Primary colours in Itten's colour wheel
Primary colours in Itten’s colour wheel

Three different models for primary colours

As is often the case, when we scratch the surface, we discover that things are not as simple as they first seemed, and we have to add some caveats. The first is that primary colours are ideal colours. In other words, they don’t exist in nature. So it’s difficult to create all the colours found in nature using primary colours, but you can create a very broad spectrum.

What’s more, there are three different primary colour models:

  • The red (R)-yellow (Y)-blue (B) model – also known as RYB – is the one that we learnt in school and is usually used in art and design. Click here for a deeper dive.
  • The RGB model (also known as the additive primary colour model) describes how light and colours work. In it, the primary colours are red  (R), green (G) and blue (B). Combining these colours in equal parts creates white light.
  • The CMYK model (also known as the subtractive primary colour model) describes how colours work in printing. The primary colours are cyan (C), magenta (M) and yellow (Y). Combining these colours in equal parts creates black (known as K).

Are you beginning to doubt your grasp of colour theory? Don’t worry. These primary colour models are used in different contexts and explain very different aspects of physical reality. Let’s find out why.

Additive primary colours and subtractive primary colours

It is usually said that there are only three primary colours: red, yellow and blue. But it’s more accurate to say that these are just one type of primary colour. There are also additive primary colours (red, green and blue), as well as subtractive primary colours (cyan, magenta and yellow).

 Additive and subtractive primary colours
Two primary colour models side by side. Left: the RGB additive model; right: the CMYK subtractive model.

So what’s the difference? The additive primary colour model describes how light works – in other words, how we see. The subtractive primary colour model, on the other hand, describes how materials work – in other words, pigments and printing.

Let’s take a closer look:

  • The RGB additive primary colours create other colours when added together. This is how our eyes work – which is perhaps why it’s easier to understand.
    For example, if we mix a beam of red light with a beam of green light, we will perceive the resulting colour as yellow.
    Adding together the three additive primary colours in equal parts will give us white light.
  • The subtractive primary colours CMYK work like special lenses that filter out some wavelengths of sunlight and reflect others. The pigments that we use in printing or painting work in exactly this way. For example, a cyan pigment is a substance that absorbs red light and reflects blue and green, which is why it appears cyan to us.
    In this case, the more we add colour, or coloured material, the darker the colour becomes. For example, when we gradually add one colour on top of another when printing. Adding the three primary colours in equal parts – thereby filtering out all wavelengths – will give us black.

From primary colours to secondary (and tertiary) colours

The traditional primary colour model  tells us that the primary colours are red, yellow and blue. And it’s a model that works very well in colour theory, design and graphics. (It was in fact popularised by Bauhaus, the legendary German art school).

Primary, secondary and tertiary colours
Primary, secondary and tertiary colours. Image:

Secondary colours

There are three secondary colours, which are obtained by mixing primary colours together. Using the traditional colour model for reference, the secondary colours are:

  • Orange. Obtained by mixing red and yellow.
  • Green. Obtained by mixing yellow and blue.
  • Purple. Obtained by mixing red and blue.

Tertiary colours

Tertiary colours Are obtained by mixing primary colours in different parts. The six tertiary colours are:

  • Red-purple. Red and blue (one part red and half part blue).
  • Blue-purple. Red and blue (one part blue and half part red).
  • Blue-green. Yellow and blue (one part blue and half part yellow).
  • Yellow-green. Yellow and blue (one part yellow and half part blue).
  • Yellow-orange. Red and yellow (one part yellow and half part red).
  • Red-orange. Red and yellow (one part red and half part yellow).

Primary colours and the colour wheel

All these colours are usually arranged in order on the colour wheel – a useful tool that is still widely used by graphic designers today.

The primary colours: the colour wheel
The primary colours: the colour wheel

The colour wheel arranges primary colours, secondary colours and tertiary colours in the shape of a circle. In doing so, the wheel shows the relationships between the different colours and helps in finding complementary colours and harmonies, in other words, colours that go well together.

It’s a tool that can help graphic designers to find the right colour palette for a project: Be it a logo, corporate visual identity or shop interior [check out our deep dive into colour palettes and useful online tools here. ].

Are you ready to experiment with primary colours and the colour wheel?