Colour Theory: The Real Primaries


So, what are the real primary colours?

You were probably taught at school that the primary colours are red, yellow and blue. If you ask Google, you might be told that the primaries red, blue and green. The further down the rabbit hole you get, the more you’ll see terms like ‘additive primaries’ and ‘subtractive primaries’ bandied around.

It can all be confusing, especially if you just want to know which are the most versatile colours to paint with. In this article, we’ll be discussing the traditional primary colours, their limitations, and which primary colours are the most versatile primaries for an artist to be carrying in their palette.


THIS ARTICLE IS ABOUT modern vs traditional primary colours
  • This article will only be dealing with Subtractive Primaries, as these are the ones that artists use. If you want to know the difference between Subtractive and Additive colours, you can read more about them here.
  • If you want to learn more about the fascinating history of the primary colours, then check out this article.

What is a Primary Colour?

Primary colours have also been known as ‘simple’ or ‘primitive colours’. In order for something to be a primary colour, it needs to meet three main criteria:

  • It has to be a pure colour that cannot be made by mixing other colours together
  • When mixed together in equal parts they’ll make black
  • By mixing them together you can make all other colours

Two more things you should know:

  • When you mix two primary colours together, you’ll get a secondary colour.
  • When you mix a primary with a secondary colour, you’ll get a tertiary colour.

Red, Yellow & Blue

also known as the traditional primaries

Red, Yellow and Blue are also known as the ‘Traditional Primaries’. Artists have commonly used these pigments to represent the traditional primaries:

  • Cadmium Red
  • Cadmium Yellow
  • Ultramarine Blue
substitutions / Pigments for a traditional Primary Palette
Primary red
  • Cadmium Red Medium
  • Alizarin Crimson
  • Pyrrol Scarlet
Primary blue
  • Ultramarine Blue
  • Cerulean Blue
  • Cobalt Blue
Primary yellow
  • Cadmium Yellow Medium

The Problem for Painters

The limitations of the red, yellow, blue palette

There are a few key problems with using red, yellow and blue as your primary colours.

Warm and cool colours

To understand the issue with the Red, Yellow and Blue primaries, you need to understand the concept of ‘warm’ and ‘cool’ colours.

When you look at the colour mixing charts above, you can see the Traditional Primaries can mix some lovely vivid oranges. This is because Cadmium Red and Cadmium Yellow are what are called ‘warm colours’ that lean towards orange.

However, the purples are desaturated and dull. There is no way to mix a vibrant bright purple using Cadmium Red and French Ultramarine; both are warm colours, which means Cadmium Red has yellow undertones, and ultramarine blue has red undertones. By mixing both together, you’re effectively mixing all the three RYB primaries together and the result is a duller, muddier colour.

Equally, while you can mix beautiful greens for foliage using Cadmium Yellow and French Ultramarine, you can’t get bright vibrant greens that would allow you to paint something like this parakeet. This is because both Cadmium Yellow and Ultramarine Blue are considered to be ‘warm’ colours, with traces of red – red is the opposite of green and, again, by mixing all three together you’re effectively mixing all three primaries together.

To compensate for these red-blue and yellow-blue weaknesses, paint makers created something called a split-primary palette. You can read more about the split-primary palette here but, in a nutshell, .

All this suggests that these three colours aren’t the most efficient primaries for an artist to be using in their palette.

The Modern Primaries

magenta, yellow and cyan

We haven’t always had access to the range of pigments we have today. Over time, brighter synthetic pigments have been discovered and turned into paints for painters to use.

Pigments for a traditional Primary Palette

Primary magentas
  • Quinacridone Rose
  • Quinacridone Magenta
Primary cyan
  • Pthalo Blue (GS)
Primary yellow
  • Hansa Yellow Medium
  • Azo Yellow

Want to know more?
If you’d like to learn more about watercolour, you might be interested in my classes.

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