The use of colour to enhance the appearance of hair has been used by people for centuries. Closely influenced by developments in chemistry and cosmetic manufacturing, the range of hair colours and products available today is huge. But before we colour our hair, we need to understand basic colour theory for hair. Here we look at how natural hair gets its colour, what depth and tone mean, and how we use colour theory to correct tones.
Basic Colour Theory for Hairdressing
All colours found in nature are a mix of the three primary colours: blue, red and yellow. These three pigments produce every known colour in the world, except black and white.
When two primary colours are mixed equally, it produces a grey. When mixed in varying proportions, the three primary colours produce a brown colour.
Our skin and hair colours are made up of various combinations and proportions of blue, red and yellow colour molecules.
Blue is the only cool primary colour – red and yellow are warm.
Primary colours in our hair vary in molecular size and pigment weight – and this is important to understand in hair colouring. Blue has the largest molecular size and pigment weight, followed by red and then yellow.
In the hair shaft, blue molecules (being the biggest) sit closest to the cuticle and is the easiest pigment to remove during colouring. Red molecules are found deeper in the cortex and are harder to remove than blue. Harder still are the yellow molecules, which sit deepest in the cortex. This is why red and yellow are harder colours to remove during the lightening process, as these pigments are deeper inside the hair shaft.
To remove red and yellow pigments, the hair shaft needs to be expanded large enough and for long enough during colouring to allow oxidation to dissipate the molecules into the air.
- More on colour theory
Natural Hair Colour
Our natural hair colour depends on melanin pigments within the cortex of the hair.
There are two main melanin pigments found in human hair, and they blend together in various amounts and proportions to form all the hair colours that we see:
- Eumelanin provides black and brown pigments and determines how dark hair is. More of this pigment present in someone’s hair gives the overall hair colour a “cool” look, like ash. Eumelanin pigments consist of all the three primary colours: blue, red and yellow.
- Pheomelanin provides red and yellow pigments. This gives rise to warmer colours in someone’s hair, like auburn, strawberry or gold.
Brown hair contains a lot of eumelanin, red hair has large quantities of pheomelanin, while light blonde hair actually contains relatively little melanin – the pale yellow we see is actually due to the keratin in the hair, rather than pigments. White and albino hair contains little or no pigment at all.
Why Hair Colour Changes
We can change our hair colour by choice through using hair dyeing products. Various chemical processes in hairdressing (like bleaching, tinting, neutralising) act on the natural pigments to change the hair’s colour. However, hair colour can change for a variety of natural reasons, including:
- Ageing can affect pigment production. As we age, melanin stops being made in our hair and new hairs grow without pigment, which is why they are white. When white hair is mixed with hair that still has colour, it creates a grey look (sometimes called “salt and pepper”).
- Blonde children can sometimes see their hair darken when they are around seven or eight years old, and have dark hair in adulthood. It darkens as melanin production increases.
- Environmental factors can impact hair colour. Oxygen in the air attacks the pigments in hair. Blue pigments are the weakest pigments and are, therefore, the first to disappear, leaving hair with the warm undertones showing through. Humidity and wind brings more oxygen to hair, and sunlight accelerates the process. Hence why our hair often lightens noticeably when on beach holidays.
- Health issues can contribute to premature greying e.g. autoimmune thyroid disease, vitiligo and ageing syndromes.
- Medication can alter natural colour e.g. certain drugs used to prevent malaria can lighten hair, while some epilepsy drugs can darken it.
- Pregnancy can darken light hair due to higher levels of hormones oestrogen and progesterone.
Describing Hair Colour
The hair colour we see consists of depth and tone. Hair also has an undercoat of colour, called undertones, which only come into play when we lighten or colour the hair.
Depth or Level
Depth simply refers to how light or dark the base colour of the hair is. It is also called level, with dark hair having a low level and light hair having a high level.
In hairdressing terms, there are 10 main levels. Numbers 1-5 are brown (black, darkest brown, dark brown, medium brown and light brown) and 6-10 are blonde (dark blonde, medium blonde, light blonde, very light blonde and lightest blonde) – see the chart below for numbering. All are neutral shades.
Tone refers to the colours we see in the hair, be they natural colours or artificially added. Tonal colours are classed as warm, neutral or cool:
- Warm tones have reds, yellow and orange in them, and are in colours such as strawberry blonde, copper and chestnut brown.
- Neutral tones have a balance of warm and cool pigments in them.
- Cool tones have blues and greens in them, and are often referred to as ash tones.
For hair colouring products, the tonal quality of the finished result is often given as part of the colour’s description (e.g. intense red, honey blonde, rich copper, light beige blonde, deep chocolate). There is also the ICC colouring system, with each tone being given a number.
Natural hair has an underlying warm tone, dictated by the amount of the pigment pheomelanin found in the hair.
Dark hair has more pheomelanin present, creating a red undertone: blondes have less, resulting in a more yellow undertone.
The undertone becomes more evident when hydrogen peroxide is used to lighten the hair. The undertone also shows through when hair is naturally lightened from exposure to the elements.
Pheomelanin is slowly oxidised during colouring and can produce those difficult-to-remove golden and orange tones in the hair. When dark hair is bleached sufficiently, it will go from having a red tinge to orange, yellow and, finally, white as the pheomelanin breaks down.
Undertone can affect the final colour result when dyeing hair.
Correcting or Neutralising Unwanted Tones
Correcting tones in hair needs an understanding of colour theory, as well as knowing what products to use and application techniques.
To neutralise an unwanted tone, the opposite colour on the colour wheel is used.
So, to remove a gold brassy look from blonde hair, we use a purple shampoo or a mauve ash toner to knock out the unwanted yellow. If the brassiness is more orange, then a blue-based product would be used. If hair has a green cast to it (sometimes caused by dyeing hair with an ash colour), a red-based product is used (yes, including tomato ketchup!).
The colours opposite each other on the colour wheel are also opposite in terms of tone – that is, warm colours neutralise cool colours, and vice versa. For example, red (warm) and its opposite colour green (cool) neutralise each other.
Completely neutralising the effect of a tone achieves a neutral shade that is neither warm nor cool.
What Media Hair and Makeup Artists Should Know
When we look at hair, the colour we see is influenced by several factors:
- The pigments (both natural and artificial) in the hair, which absorb some light and reflect others;
- The brightness and colour of the light in which we are looking at the hair;
- To some extent, the clothing worn by the person, or the environment they are in.
So, as well as knowing your colour theory, you should also consider other aspects of working in film, TV or theatre. Understand how lighting affects colour, how the colour and material used for costumes and sets can reflect onto hair and skin, and how different hair (from natural to wigs made from various types of hair) can look on camera or stage.