CI (Color Index)
Plural: CIs (Color Index designations)
CI (Color Index) definition
CI (Color Index) is an international identification system that gives every pigment and dye a unique code, allowing artists and manufacturers to know exactly which coloring substance is inside a paint, regardless of the brand or marketing name.
- CI (Color Index) stands for Color Index, an internationally recognized classification system that assigns a unique identifier to every commercially used pigment and dye. In artists’ paints, the Color Index code reveals the actual pigment used in the formulation, making it possible to compare paints from different manufacturers.
A complete Color Index name consists of:
- A prefix indicating the type of colorant:
- P = Pigment
- A = Acid dye
- B = Basic dye
- D = Direct dye
- S = Solvent dye
- V = Vat dye
- …and several other categories.
- A color abbreviation, such as:
- R = Red
- Y = Yellow
- B = Blue
- G = Green
- Br = Brown
- Bk = Black
- W = White
- O = Orange
- V = Violet
- A number identifying the specific pigment or dye within that color family.
For example:
- PB29 = Pigment Blue 29 (French Ultramarine)
- PR108 = Pigment Red 108 (Cadmium Red)
- PY35 = Pigment Yellow 35 (Cadmium Yellow)
- PBr7 = Pigment Brown 7 (Raw Umber, Burnt Umber, and other natural earth pigments)
- PW6 = Pigment White 6 (Titanium White)
Many professional paints contain a single pigment, while others contain two or more Color Index pigments. For example, a tube labeled Sap Green might contain PY150 + PG7, while another brand’s Sap Green could use an entirely different combination. The Color Index allows artists to identify these differences.
Examples
Example 1: Two brands both sell “Permanent Alizarin Crimson,” but one contains PR177 while the other contains PR264 + PV19. The Color Index reveals that they are different paints despite having the same marketing name. Example 2: An artist looking for a clean, predictable mixing color may choose a paint labeled PB15:3 because it contains only one pigment instead of a blend.
Context
The Color Index is one of the most valuable pieces of information printed on a paint tube. Paint names are not standardized and vary widely between manufacturers, but the Color Index code identifies the actual pigment inside. Understanding these codes helps artists compare products, predict color mixtures, evaluate permanence, and select single-pigment paints for cleaner color mixing.
Core Principles
- Color names are marketing terms; Color Index codes identify the actual pigment.
- The same paint name can contain different pigments depending on the manufacturer.
- The same pigment may appear under many different commercial names.
- Single-pigment paints generally produce cleaner, more predictable mixtures than multi-pigment blends.
- Learning common Color Index codes (such as PB29, PB15:3, PR108, or PY35) allows artists to make informed choices independent of brand.
Derivation
The Color Index was developed by the Society of Dyers and Colourists (SDC) in the United Kingdom together with the American Association of Textile Chemists and Colorists (AATCC). It serves as the international standard for identifying pigments and dyes used in industries ranging from fine art and printing to textiles and plastics.