Colour Index International
Created in 1924, the Colour Index International is a comprehensive database of pigments and dyes, published by the Society of Dyers and Colourists and the American Association of Textile Chemists and Colorists. While colorants are often sold under a wide range of proprietary and generic names, the Colour Index provides a standardized naming system used by manufacturers and consumers worldwide.
For artists, this system can be an invaluable tool. It allows them to look beyond marketing names and identify the actual pigments used in a paint, making it easier to understand colour behaviour, permanence, compatibility, and mixing characteristics across different brands.
What Is a Pigment?
Pigments are finely ground coloured powders that are mixed with a binder—such as linseed oil, gum arabic, or acrylic polymer—to create artist paints. Dyes, by contrast, are soluble; they dissolve in the binding medium and chemically bond with the material being coloured, which makes them especially suitable for textiles.
Pigments are insoluble. Rather than dissolving, they are suspended within the binder, remaining as discrete particles that give paint its colour, opacity, texture, and lightfastness.
How Does the Colour Index Work?
Unlike colour-matching systems such as Pantone or the Munsell System, the Colour Index International classifies dyes and pigments according to their chemical composition, rather than the specific hue, value, or chroma they produce.
Each pigment is assigned two identifying codes: a Colour Index Constitution Number and a Colour Index Generic Name Code. For example, Ultramarine Blue is classified under CI 77007 (its Constitution Number) and PB29 (its Generic Name Code).
The Colour Index Generic Name Code is the identifier most familiar to artists. It typically appears on paint tubes, bottles, and colour charts, and allows artists to recognise a pigment regardless of the marketing name used by a manufacturer.
The Generic Name Code is structured as follows:
-
The first letter P stands for Pigment
-
The second letter indicates the colour family (e.g. B = Blue, R = Red, Y = Yellow, G = Green, V = Violet, Bk = Black)
-
The number identifies the specific pigment within that colour family
For example, PB29 always refers to Ultramarine Blue, even though its appearance may vary slightly between brands due to differences in grinding, binders, or formulation.
By understanding these codes, artists can make informed decisions about colour mixing, lightfastness, granulation, staining, and pigment compatibility—making the Colour Index an essential reference for anyone who wants greater control over their materials.
Why Is the Pigment Colour Index Useful for Artists?
Becoming familiar with the Pigment Colour Index allows artists to look beyond colour names and understand what their paints are actually made of. This knowledge can significantly improve material choices, mixing control, and long-term results. Here are some of the key reasons it is so useful.
The Pigment Colour Index Provides Insight Into How Different Paints Behave
Every pigment has its own inherent characteristics, including transparency or opacity, tinting strength, granulation (in watercolour), drying rate, lightfastness, and permanence. These properties have a direct and often dramatic impact on how a paint performs in practice.
A pigment’s physical structure and chemical composition determine how it behaves on the page or canvas. While the underlying chemistry can be complex, recognising which pigments are naturally staining, granulating, opaque, or slow-drying allows artists to make informed choices and use their materials more intentionally.
By identifying pigments through the Colour Index, artists can predict how a paint will behave before using it, rather than relying solely on brand names or colour charts. This leads to more consistent results and a deeper understanding of one’s palette.
The Pigment Colour Index Tells You How Many Pigments Are in the Paint
The number of pigments in a paint matters greatly to many artists. Single pigment colours — paints that contain only one pigment — are generally considered best for mixtures because mixing multiple pigments together results in muddier colours. If single pigment colours are important to you, the Pigment Colour Index is invaluable for ensuring you are using a single-pigment version of a colour.