What colours are, whether they are properties of substances or light, manifestations of radiant energy, pure subjective experiences, or results of interactions between the perceiving subject and any of the above is a matter of ongoing scientific and philosophical debate. In any account it must be recognised that colours are, ultimately, a visual phenomenon.

Colour plays many roles in our lives: it keeps us safe by signalling danger or helping us decide whether food is safe to eat; it helps us navigate; it brings us joy as we watch a beautiful sunset. Noticing, describing and understanding the key roles that colour plays in our lives helps us establish a strong relationship with our surroundings, and deeply engage in the world.

Colour can impact us in many ways. It can affect us viscerally, impacting how we feel in ways we cannot fully describe with words. We may have strong responses to colours, have various colour preferences, have emotional responses to colours, have associations with colours (which are likely influenced by our culture and environment) and use colour symbolically to communicate how we feel. Our human relationship with colour is complex, and there is no ‘one-size-fits-all’ connection between specific colours and emotions, which applies universally to all people, across all cultures.

Just as there are basic colour terms used to describe the hue of a colour, such as blue and green, there are basic colour modifier terms used to describe variations of a hue. The three most basic modifiers organize, or group, colours according to whether they appear to be lighter, darker or duller than the most vivid hue.

The Colour Literacy Project introduces the term character to describe these variations. The four basic character groups are vivid (vibrant/bright), pale (pastel/light), dark (deep), and muted (muddy/dull). By describing colours with modifiers at the earliest stages of colour education, students enhance both their perceptual colour discrimination and their verbal descriptive capabilities.

Similar terms for character are ‘Nuance” used by the Natural Colour System, and “Image” used by the Nippon Color Institute.

Note: Hue and character are appearance language terms. They are related to, but distinguished from, the mixing language terms of pure, tint, shade and tone.

Basic 3D models of colour show colour relationships in three directions or dimensions:

1. Colours related by hue (e.g. the hue circle)

2. Colours related by lightness (e.g. comparing the light reflected by the colour to a grey scale between black and white)

3. Colours related by chroma (e.g. the amount of visual distance from the grey scale)

By organizing colours in 3D colour models at an early stage of colour education, rather than beginning with the 2D hue circle, students better appreciate colour variations and relationships.

Note: Another term often used for lightness is value. Other terms related to chroma are saturation and intensity (but do not mean the precisely the same as chroma).

Our experience of colour starts with light. Although we may sometimes dream in colour, or remember our experiences of colour, most of our daily colour experiences begin with light. Light can come to us directly, from sources like the Sun or a computer screen), or light can come to us indirectly, after it has interacted with some kind of object (like an apple or a splotch of paint). When light activates our visual system, we experience a colour perception.

Although it seems as if colour is a property of the physical world that is ‘out there’, colour is ultimately a perception which results when light enters our eyes and activates our whole visual system.

There are many variations in the way we perceive colours. Some people have limited colour vision, and see only a fraction of colours seen by people with full colour vision. Other people with synesthesia can experience colours when other senses are activated.

There are many external contexts that affect our perception of colour. Lighting plays a major role, and the surrounding colours can also have an influence on how we perceive colours.

In addition to the various external contexts which impact the colours we see, there are several internal contexts which also can play a role in how we perceive colour. Our memories, experiences, culture and language all contribute to the overall context for colour perception.

Colour is a non-verbal language, and can signal things like danger or various types of social behaviours in the natural world. Humans have many cultural associations with colours, which are often thought to have universal symbolic meanings, however colour symbolism and meaning are complex ideas, intertwined with history, nature, culture and context. Such associations often simply connect the hue of a colour with a particular emotion or idea. However, associations linking the character of the colour. (e.g. whether it is vivid, pale, dark and muted) with an emotion or idea may more strongly convey the connection.

Colour is often used by artists and designers to represent emotions and/or enhance the messaging of a particular idea or concept.

It is important to recognize that we do not mix colours, rather we mix coloured media. Colours are perceptual experiences, and can’t be mixed, but colorants or coloured media can.

There are many mixing processes including:

• Additive mixing of coloured light sources

• Optical mixing on display screens (e.g. computer or phone)

• Subtractive mixing of paints, inks, dyes, etc.

• Optical mixing using spinning disks (via temporal averaging), or Pointillist painting (also called partitive mixing)

In each type of mixing process, the media interact with light in slightly different ways. This means that the light which is sent to our eye depends both on the mixing process and on the specific medium used. Thus the perceived colour of a mixture depends both on the process and the medium.