Colour Theory

Author Peter Weatherill

An understanding of colour theory and how it works is of great importance to artists who use coloured pencil. 

There are many books available that go into the technicalities of colour and a good Internet place to look for very detailed explanations of colour theory is the site built by Bruce MacEvoy, Bruce guided me in my early explorations of watercolour many years ago, and his site now sees over 2500 visitors a day. The Handprint web site specialises in watercolour, but the theory part is very valuable for any artist.

I have not copied Bruce's work, but I have written up a page here that provides what I hope will be a simple explanation of how colour works and why we need to understand it to present satisfactory artwork in coloured pencil. 

Please bear in mind that my explanation takes the subject simply. It is intended as a basic guide to understanding - not a thesis for experts. To explain things as simply as possible I need to ignore some complications.

Coloured light behaves quite differently to coloured pigment

If you add coloured lights together you get white (or progressively reach white as you add more and more colours).

This is known as Additive colour.

If you add pigments together, you get nearer and nearer to black.

This is known as Subtractive colour.

When we mix colours with paint we need to think in terms of Subtractive colour.

Additive colourAdditive colour
Subtractive colourSubtractive colour
Simple colour wheelColour wheel

But at the same time we need to be aware that coloured light handles differently and this will have an effect on how we see coloured pencil work which relies on layers of colour and filtered light through those layers.

I am assuming that you know the three primary colours.

  • Yellow - at the top of the colour wheel
  • Blue - at 8 o'clock
  • and Red - at 4 o'clock

Mixing pure Yellow and pure Blue (which don’t exist in life) would produce the pure Green shown in between them.  Similarly mixing the Red and Blue should produce Purple and mixing the Yellow and Red should produce Orange.

This would be so in a perfect world, but this isn’t a perfect world.

Why do we see different colours?

Light reflecting off white paperLight reflects off white paper and we see it as white

White light falls on white paper and we see white paper. All the light which falls on the paper is reflected - and we see the paper as white. 

White light is made up of a whole collection of coloured light - such as we see in a rainbow - with a spectrum of colours ranging from Red through Orange -  Yellow - Green - Blue - Indigo - to Violet.  

There are a host of variations of these colours in between. In addition, Infra Red at one end and Ultra Violet at the other, exist but can’t be seen by the naked eye.

Pigments are natural (inorganic - made from rocks and stone) and manufactured (organic - often dyes from chemical processes). These materials affect the way light is absorbed and reflected from a surface.  They may be pure pigments but they are not pure colours.

A ‘White’ pigment (like Titanium Dioxide) allows all the light to reflect, the blend of colours making up white light are unchanged. The eyes see white paper.

If that ‘bundle’ of coloured light we see as ‘white’ falls on a surface that has been treated with colour, we see the surface as coloured.


Because the pigment absorbs some of those colours from the white light and only allows some colours to reflect and be seen by the eye.

If it only absorbs a small amount of the light, we see the colour as light or bright. If the surface absorbs a lot of the light and a only small amount is reflected, we see the colour of the surface as dark.


That image shows green paper and red light - how come?

What I am showing here is that the pigmented material is absorbing all the yellow and blue light from the white light (making green) and only showing reflected red light.

So, taking it at its most basic...

If you shine a green light at a piece of paper and it appears to have red colouring, all the green light will be absorbed by the pigment and the coloured parts of the paper will appear to be black or dark.

I am not sure this illustration of a red fish with a green filter over part of the image is an ideal example, but it shows how the original red is killed by a later layer of green transparent colour over the top. 

The lower slices of colour in the example enable you to see more clearly how a thin layer of transparent green makes a dramatic difference to the original red colour, and produces a darker version of the green. 

The darkening effect is the result of using complementary colours. 

This is also illustrated by the quick coloured pencil sketch of a red oval overlayed by a green shape. Where they overlap the area is darker.

What are complementary colours?

If you look again at the colour theory wheel you will see that red lies on the exact opposite side of the wheel from green, which is a mix of yellow and blue (the other two primaries). 

Red is the complementary colour of green. In the same way, blue is the complementary of orange and yellow is the complimentary of violet. 

But this is the real world and colours in real life don't quite behave like this. We don't have 'pure' colours - we have colours made from materials that are close to - but not quite the same as pure colours. 

We have yellows that are green-ish; we have reds that are purple-ish. Colours in a tube of paint or a coloured pencil are a blend of colours so they will not always behave as the rules of colour theory would have us expect. 

Some pigments are strong and will provide strong blends (i.e. Phthalo Green and Blue). Other colours are light on tinting strength (many yellows). So equal amounts of different pigments do not have the same effect when mixed. 

A regular mix in watercolour for a very dark grey/black consists of Ultramarine Blue (a dark blue with purple in it) and either Burnt Sienna or Burnt Umber (dark red with some orange). By adding a little more of one or the other colour in the mix you can get a whole raft of shades of dark blues, blacks, greys and browns. 

How does this relate to coloured pencils?

Let's get back to seeing how this colour theory relates to coloured pencils. 

With wax type coloured pencils we are layering colour to build up the exact tint and depth of colour we want. 

If we use a complementary colour in a layer it will have the effect of darkening the later layer. The white natural light passing through a green top layer will become filtered to become green light and suddenly find itself being absorbed by the 'red' layer underneath. We will see a much darker colour as so much light is being absorbed.

Depending on the strength of the pigment you will see differing results. A strong pencil blue over a weak yellow pencil  will have little effect in making a green. Just as mixing an equal amount of light lemon yellow paint with Phthalo blue will not produce a mid green - if you are lucky it might just achieve a slightly greenish blue. You need to know that colours need to be balanced in mixing or blending. 

This is why watercolour artists always start with their weakest colour when mixing paint, and add small amounts of a strong colour to make their mixture. Done in reverse, they would need a bucket to put their mixture in!

The first layer of colour

With coloured pencil on white paper we have an extra factor to consider. The first colour to be put down on the fresh white paper will have 70% effect on the final colour (provided later layers are transparent - some colours are more opaque). 

Later layers will have progressively less and less an effect as the wax begins to acquire a polish and less and less colour is taken up by the surface. If we use a weak colour as the foundation, this will give it a greater power in any blended colour - though a lot will still depend on the strength of later colours applied. 

If we underpaint coloured pencil with watercolour pencil we can use complementaries to get very useful darks (reds under greens are a case in point for landscape artists). If we use a wash of dark red underneath areas that will be green later, we gain very vibrant greens once the green coloured pencil is applied. 

Complementary colours also have a great effect when they are used with the two colours not mixed, but in close proximity. Here the effect is to have the colours vibrate together in the eye and become a point of focus in the picture. 

Using colour theory to decide which pencils to use

When you need to decide which coloured pencils to use in a mix there are a number of factors that influence your decision. 

  • The colours that are available in the tin
  • What ingredients are those colours are made from
  • What colour you are trying to achieve
  • Which colours would be likely to make the best layering options

Many brands of pencil come in large selections of up to 120-150 colours. Do we need them all? Having a large number can first appear wonderful, but a much better effect is achieved by layering different colours rather than using a single pencil of the 'right' colour from the box.

Using color theory to ensure that the colours used in our artwork are harmonious means limiting our selection to those that will work together nicely. But how do we decide that?

The colours in the pencils are not pure pigments. The pigments can come from natural sources such as umber, sienna or ochre. Or they can be chemically produced as is the case with many modern lightfast and permanent colours, such as Phthalo blues and greens, Arylide yellows or the Quinacridone orange and rose colours.

Your pencil tin will likely include a range of different yellows, reds, blues, greens and many others that are 'not quite' the same but very close to each other. 

So why do we need more than one of each primary colour?

  • Ideally you will find a warm yellow that leans towards being orange, along with a cool yellow that has a greenish tinge to it. 
  • You will also need a warm blue that leans towards purple and a cooler one that veers towards green
  • Lastly your reds can be on the orangey or on the bluish/purple side of the colour wheel

The example below shows the use of 6 colours - a warm and cool of each primary. I layered the two warms together and  two cools together. Then mixed things up by taking each of the cool colours and mixing it with each of the warms. You will see that some mixes produce clear colours (the warm yellow and warm red for example) and some produce muddy tones (the warm yellow and warm blue). None of these are wrong - if that was the result I wanted to achieve! 

If we wish to produce the purest and brightest greens from yellow and blue colour theory tells us that the best place to start is by picking a yellow with a green bias (lemon yellow is a good example) and a blue which leans towards green (cerulean). 

If on the other hand we pick the orangey yellow and a warm blue that leans towards purple the green content of the colours we are layering is low and we will get a dark or 'dull' green. This may be the perfect choice for certain areas of a landscape.

If we select one ideal and one less suitable colour to mix, such as the orange yellow (with little green in it) and a greenish blue (cerulean again) we may well get a green that is closer to olive green with a higher brown content. 

Avoid mixing too many colours together

A good rule in deciding what colours to use, is to avoid mixing too many colours together. If you do, the impurities and peripheral colours in the pencils will add together to produce a dirty, dull result rather than a clean, bright colour. 

Watch out for "earth" colours like yellow ochre, raw and burnt sienna and umber, etc. These are generally ground pigments from natural earths. Blending colours with them will speed up the process of achieving coloured mud - after all these earth colours are virtual mud anyway! If you have tried watercolour before you will be familiar with this!

The best colours are made with only one pigment. But pencil manufacturers rarely use a single pigment per pencil. Each one can contain a mix of pigments to produce the pencil "colour". Sadly, they never tell us which mix of pigments have been used. The more we use them, the more we will learn what "hidden' colour is also included in each pencil. 

If we attempt to mix two pencils and get an unexpected effect we can then surmise that one or other of them contains a little of a different colour, most likely the "missing" primary.

Therefore try not to mix more than three pencil colours together as doing so may well give rise to problems especially if you are working with watercolour pencils where the pigments are physically mixed rather than being layered on top of each other.

To Summarise

Colour Theory teaches us that there are three primaries, which mixed together create three secondaries. 

We have learned that our pencils do not necessarily contain pigments that are true primaries but instead they have a bias towards one or other of the other primaries. This means that layering them does not always provide a clear bright mix that we can name as orange, purple or green. 

Each 'primary' can be labelled warm or cool depending on which of the other primaries it leans towards. Knowing this, we can choose whether we want to mix warm or cool colours, or a mix of both in an area of our artwork. 

We also learned a little about complementary colours and how they can be used to darken or dull down our layered areas. 

Hopefully this introduction to colour theory will help you to get the results you want when working with coloured pencil.

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