Understanding the Color Index Generic Name Code for Better Colour Mixing in Art

12 hours ago
4 min read

I love colour mixing, it fascinates, stimulates and challenges me. In a workshop yesterday I was explaining the Colour Index System and how it can help understand colour mixing, and lead to more confident and satisfying painting.

Paint names can be confusing or misleading, and the same color name might represent different pigments across brands. This is where the Colour Index Generic Name Code becomes an essential tool. It offers a standardized system to identify pigments, helping artists make informed choices and achieve consistent results in their work.

What Is the Colour Index Generic Name Code?

Finding the Colour Index info

The Colour Index Generic Name Code, often called the Colour Index International (C.I.) system, is a standardised classification for pigments and dyes. It assigns each pigment a unique code based on its chemical composition rather than its commercial name. This system was developed to reduce confusion caused by marketing names and to provide a clear reference for artists, manufacturers, and scientists.

Each pigment receives a code starting with a letter indicating the pigment type:

P for Pigment
D for Dye

This is followed by a letter representing the color family, such as:

R for Red
B for Blue
Y for Yellow
G for Green
V for Violet
O for Orange
Br for Brown
Bl for Black

Finally, a number identifies the specific pigment within that family. For example, PBr7 refers to a specific brown pigment, while PB29 identifies a particular blue pigment.

Why the Colour Index Code Matters to Artists

Consistency Across Brands

Paint manufacturers often use different names for the same pigment or the same name for different pigments. For example, "Cadmium Red" might vary slightly in hue or opacity depending on the brand. By checking the Colour Index code, artists can ensure they are buying the exact pigment they want, regardless of the brand.

Understanding Pigment Properties

Each pigment has unique characteristics such as opacity, lightfastness, toxicity, and mixing behavior. The Colour Index code helps artists research these properties accurately. For instance, PR108 (Cadmium Red) is known for its opacity and lightfastness, while PR254 (Pyrrole Red) is more transparent but equally lightfast.

Avoiding Toxic Pigments

Some pigments contain toxic elements like cadmium or cobalt. The Colour Index code allows artists to identify these pigments and choose safer alternatives if desired. For example, PY37 (Cadmium Yellow) contains cadmium, while PY74 (Benzimidazolone Yellow) is a non-toxic alternative.

How the Colour Index Code Helps with Colour Mixing

Predicting Mixing Results

Knowing the exact pigment helps artists predict how colors will mix. Some pigments are staining, meaning they absorb into the surface and are hard to lift, while others are non-staining and easier to manipulate. Mixing a staining pigment with a non-staining one can affect the final texture and appearance.

For example, mixing PB15 (Phthalo Blue), a strong staining pigment, with PY3 (Hansa Yellow), a transparent pigment, produces a bright green. But mixing PB29 (Ultramarine Blue), which is less staining, with the same yellow results in a more muted green.

Avoiding Muddy Colors

Certain pigment combinations produce dull or muddy colors. The Colour Index code helps artists avoid mixing pigments from the same color family or those with similar undertones that neutralize each other. For example, mixing two reds like PR108 and PR254 can deepen the red but mixing PR108 with PB29 (Ultramarine Blue) can create a rich purple.

Building a Balanced Palette

Artists can build palettes with pigments that cover a wide range of hues and mixing possibilities by selecting pigments with different Colour Index codes. This approach ensures vibrant mixes and reduces the risk of color bias.

Practical Tips for Using the Colour Index Code

Check labels carefully: Most quality paint tubes or pans include the Colour Index code near the pigment name.
Research pigments: Use online resources or pigment databases to learn about the properties of each pigment code.
Test mixes: Create small swatches mixing pigments with known Colour Index codes to observe their behavior.
Choose alternatives: If a pigment is toxic or unavailable, find substitutes by matching Colour Index codes.
Keep a pigment journal: Record your favorite pigments and their codes along with notes on mixing results.

Examples of Common Pigments and Their Codes

| Pigment Name | Colour Index Code | Characteristics |

|--------------------|-------------------|---------------------------------|

| Cadmium Red | PR108 | Opaque, lightfast, toxic |

| Quinacridone Magenta | PR122 | Transparent, vibrant, lightfast |

| Ultramarine Blue | PB29 | Semi-opaque, granulating |

| Phthalo Blue | PB15 | Transparent, staining, intense |

| Cadmium Yellow | PY37 | Opaque, lightfast, toxic |

| Hansa Yellow | PY3 | Transparent, bright |

| Titanium White | PW6 | Opaque, high covering power |

| Burnt Sienna | PBr7 | Semi-transparent, warm brown |

How to Incorporate the Colour Index Code into Your Art Practice

Start with your current paints: Identify the Colour Index codes on your tubes or pans.
Research each pigment: Understand its mixing behavior, opacity, and toxicity.
Plan your palette: Choose pigments with complementary properties and diverse codes.
Experiment with mixing: Use pigment codes to predict and test color blends.
IMPORTANT!! Document your findings: Keep notes on how different pigments interact. Nothing worse than a finding a beautiful colour, then forgetting how you made it.

Benefits Beyond Mixing

The Colour Index code also helps artists when:

Buying new paints: Ensures you get the exact pigment you want.
Communicating with other artists: Provides a clear reference for pigment choices.
Restoring artwork: Identifies pigments used in older works.
Teaching color theory: Offers a scientific basis for understanding pigments.