Colour is all around us. We sense it intuitively, yet behind every shade lies a fascinating interplay of physics, chemistry and perception. In this article, we explore primary, secondary, and tertiary colours through the history of pigments, the basics of colour theory and practical use. We also look a little deeper: what exactly is the difference between colour and pigment? And how are they connected?
Colour versus pigment: what’s the difference?
Colour is essentially light. It’s a property of light waves perceived by our eyes within the visible spectrum. Red, for instance, has a longer wavelength than blue. Colour exists only when light is present to reflect or transmit. Pigment, on the other hand, is matter. It consists of solid particles (often powders) that absorb part of the light and reflect the rest. The reflected portion determines the colour we see. Pigment is therefore the physical source of colour. Without pigment or another colour source such as dye or light, there’s no visible colour difference in a material.
In short:
colour = an optical phenomenon (light and perception)
pigment = a physical substance that reflects colour
The relationship between colour and pigment is similar to that between music and an instrument: pigment is the instrument, colour the sound it produces.
Primary colours and their pigments
The traditional primary colours (red, yellow, blue) form the basis of the RYB colour wheel and cannot be created by mixing other colours. But what does this mean in terms of pigment?
Historically, the pigments available determined how artists worked. The brightness and durability of a colour depended on the pigment itself rather than on the abstract idea of red. Some reds, such as vermilion, were rich and opaque, while others proved unstable or faded quickly.
This led to an important insight: colour theory may be universal, but pigments are not. Their limitations force artists to make choices between purity, blendability and longevity.
Secondary colours: a chemical compromise
Secondary colours (orange, green, purple) are created by mixing primaries. In theory this is simple, but in practice the outcome depends heavily on the quality and purity of the pigments involved.
Not every blue pigment combines well with every red to produce purple. Some mixtures become dull or muddy, while others remain vibrant. This is because pigments don’t reflect a single wavelength; they reflect a spectrum containing both desirable and undesirable components.
As a result, pigment mixtures rarely behave predictably. The final hue is always influenced by each pigment’s absorption and reflection profile. This is why artists often have favourite pigment pairings or intentionally choose muted pigments for deeper, warmer tones.
Tertiary colours: nuance through pigment variation
Tertiary colours are formed by mixing a primary with a secondary, such as yellow-green or red-violet. In theory, the range of possible tertiary colours is limitless. In practice, the effect depends entirely on:
- the type of pigment
- the mixing ratio
- the binder or medium in which the pigment is suspended
Tertiary colours are often richer and more nuanced, precisely because of the interaction between different pigment layers. Some particles remain on the surface while others sink into the medium, creating depth and vibrancy, especially in traditional techniques like glazing.
Practical applications and intentional choices
In art education and creative practice, colour is often taught as a tidy system: the colour wheel, complementary contrasts, warm and cool tones. But in real-world use, artists and designers focus primarily on the behaviour of pigments:
- How does it mix?
- Is it transparent or opaque?
- How quickly does it fade?
- How does it react to light or humidity?
This knowledge shapes how colour is applied. A bright blue from a printer (CMYK) is entirely different from cobalt blue in oil paint. The theory may be the same, but the material and therefore the result changes drastically. Even in colour therapy or personal colour analysis, this distinction matters, as the physical experience of pigment on a canvas can evoke a very different response from a colour on a screen or garment. Colour and pigment are two sides of the same coin. Colour concerns light and perception; pigment concerns materials and technique. Whether you’re creating, designing or teaching, understanding both is essential. Only then can you work deliberately and confidently with the power of colour.