Complete Guide to Hair Colorimetry Basics

Why do some formulas work perfectly while others turn into disasters? The answer lies in colorimetry.

If you’ve been in the salon for a while, you know that formulating color isn’t just about mixing numbers. Behind every result is a precise science that, when you understand it, transforms the way you work. The ashy blonde that turns out perfect. Gray coverage without surprises. Balayage with flawless transitions.

In this guide, we’ll build the foundations of hair colorimetry together. From color theory to its practical application in the salon. Everything you need to formulate with confidence.

What is Hair Colorimetry

Hair colorimetry is the scientific study of color applied to hair. It combines physics, chemistry, and visual perception to understand how color behaves in the hair fiber.

In practical terms, colorimetry allows you to:

Predict results before applying the dye
Diagnose your client’s hair correctly
Formulate with mathematical precision
Correct when something doesn’t turn out as expected

The difference between a colorist who “tries to see what happens” and one who formulates with confidence is right here. In mastering these fundamentals.

The Three Pillars of Colorimetry

Everything in colorimetry is built on three fundamental concepts:

Pillar	What It Studies	Practical Application
Color theory	How colors interact	Neutralization, mixing
Level system	Hair lightness/darkness	Diagnosis, formulation
Color chemistry	How dyes and developers work	Timing, ratios, damage

Let’s dive deeper into each one.

Color Theory: The Color Wheel

The color wheel is your map for understanding how colors relate to each other. Based on the Munsell color notation system, which organizes colors by hue, value, and chroma, this tool is fundamental for any colorist. Although it may seem like abstract theory, you use it every day when neutralizing orange or balancing violet.

Primary Colors

The three colors that cannot be created by mixing others:

Blue: The coolest, present in ash tones
Red: The warmest, appears in dark underlying pigments
Yellow: Luminous, appears in light underlying pigments

Secondary Colors

Formed by mixing two primaries:

Orange = Red + Yellow
Green = Blue + Yellow
Violet = Blue + Red

Complementary Colors

Here’s the key to neutralization. Opposite colors on the wheel cancel each other out:

Color	Complementary	Practical Use
Orange	Blue	Neutralize warm bleached hair
Yellow	Violet	Tone brassy blondes
Red	Green	Cancel red bases
Green	Red	Correct green tones

When you mix a color with its complementary in equal amounts, you get a neutral tone (brown or gray, depending on the level).

Pro tip: Never use pure complementaries at 100%. Always dilute them with a natural tone to avoid muddy results.

The Level System: 1 to 10

The tone level indicates how light or dark a color is. It’s a universal system that goes from 1 (black) to 10 (platinum blonde).

Level Chart with Underlying Pigments

Each level has an associated underlying pigment. This is the pigment that appears when you lighten hair:

Level	Description	Underlying Pigment
1	Black	Dark red
2	Very dark brown	Red
3	Dark brown	Red-orange
4	Medium brown	Orange-red
5	Light brown	Orange
6	Dark blonde	Yellow-orange
7	Medium blonde	Orange-yellow
8	Light blonde	Yellow
9	Very light blonde	Pale yellow
10	Extra light blonde	Very pale yellow

This knowledge is fundamental. If you lighten a level 4 and orange-red appears, it’s not a mistake: it’s chemistry. And knowing this, you can neutralize it correctly.

To dive deeper into how to correctly identify levels, check out our complete guide to hair color levels.

How to Identify Natural Level

Misdiagnosing the level is one of the most common mistakes. Here’s the correct process:

Proper lighting: Natural or neutral white light. Never warm salon light
Correct zone: The nape, less affected by sun
Dry hair: Wet hair appears darker
Compare with swatches: Don’t rely on your eye alone
Consider gray hair: Can “raise” the perceived level

The 4-Level Rule

Oxidative dye can lighten a maximum of 4 levels on natural hair.

Examples:

Level 3 → maximum level 7
Level 5 → maximum level 9
Level 6 → maximum level 10

To lighten more, you need pre-lightening.

The Reflect System: Understanding Color Codes

After the level comes the reflect. That number after the decimal point that defines the color’s hue.

Universal Reflect Numbering

Although it varies slightly between brands, the general system is:

Number	Reflect	Characteristics
.0	Natural	Base without dominant reflect
.1	Ash	Blue/violet, cool
.2	Iridescent/Violet	Pure violet
.3	Gold	Warm yellow
.4	Copper	Orange/copper
.5	Mahogany	Red-violet
.6	Red	Pure red
.7	Matte/Green	Matte base, anti-red

How to Read Color Codes

In a code like 7.13:

7 = Level (medium blonde)
1 = Primary reflect (ash)
3 = Secondary reflect (gold)

Result: Medium blonde ash with golden undertone (a warm ash, less cold than a pure 7.1).

Reflect Mixing Rules

Cool reflects (.1, .2) neutralize warm tones
Warm reflects (.3, .4, .5, .6) add luminosity
Natural base (.0) softens and adds body to the color
Never mix more than 3 reflects: The result will be muddy

Developers: The Other Half of the Equation

Developer isn’t just “the liquid you mix with the dye.” It’s an active component that determines the final result. According to research from the Society of Cosmetic Chemists, hydrogen peroxide concentration directly affects both lift and damage to the hair fiber.

Volumes and Lifting Power

Volume	Concentration	Lift	Main Use
10 vol	3%	0-1 level	Deposit, toning
20 vol	6%	1-2 levels	Standard, gray coverage
30 vol	9%	2-3 levels	Highlights, dark bases
40 vol	12%	3-4 levels	Bleaching (with caution)

The golden rule: use the minimum volume necessary for the result. More developer doesn’t mean better results, it means more damage.

To understand when to use each volume, check out our guide to developer volumes.

Dye to Developer Ratios

Technique	Ratio	Notes
Global color	1:1	Standard
High-lift tints	1:2	More power
Semi-permanent	1:1 or 1:1.5	Brand dependent
Color bath	1:2 or 1:3	Dilution

Neutralization: The Art of Correcting

Mastering neutralization is what separates a good colorist from an excellent one. It’s the practical application of everything above.

Basic Principle

Complementary colors cancel each other out. But the key is in proportions:

Slight unwanted tone: 1/4 corrector
Medium unwanted tone: 1/3 corrector
Intense unwanted tone: 1/2 corrector

Practical Cases

Neutralizing orange (levels 5-6):

Use ash reflects (.1)
Formula type: 7.1 (30g) + 7.01 (20g) + 7 natural (10g)
The natural touch prevents it from looking “muddy”

Neutralizing yellow (levels 8-9):

Use violet reflects (.2)
Specific toners
Short time: 5-15 minutes maximum

Neutralizing red (levels 2-4):

Never use pure green
Use ash with matte base (.13 or .31)
Requires more time and patience

For specific neutralization techniques, check out our guide to neutralizing unwanted tones.

Professional Diagnosis: Before Formulating

Before mixing anything, you need information. A complete diagnosis includes:

1. Hair History

Key questions:

When was the last dye applied?
What brand and color did they use?
Have you ever used henna?
Have you had highlights or bleaching?

2. Current Condition

Natural level: At the root zone
Level in mids and ends: May differ from previous treatments
Porosity: High absorbs quickly, low needs more time
Elasticity: Indicates fiber health
Gray percentage: Affects formulation

3. Desired Result

Show visual examples
Agree on realistic expectations
Document in writing

The most common diagnosis mistakes are in our guide on color formulation errors.

Step-by-Step Formulation

With the complete diagnosis, formulation follows a logical process:

Step 1: Determine Target Level

What level does the client want to reach? Is it achievable with dye or does it need bleaching?

Step 2: Calculate Level Difference

Target level - Current level = Levels of difference

This determines the necessary developer.

Step 3: Consider the Underlying Pigment

What pigment will appear when lightening? Do you need to neutralize it?

Step 4: Choose Reflects

Primary reflect: The dominant one
Secondary reflect: Modifies or balances
Natural base: Softens if necessary

Step 5: Calculate Proportions

Adjust quantities based on:

Intensity of neutralization needed
Hair length
Hair density

Practical Example

Client: Natural level 5, wants cool medium blonde (7.1)

Difference: 7 - 5 = 2 levels → 20 vol developer
Underlying pigment levels 5-7: Orange → Needs ash
Formula: 7.1 (40g) + 7.01 (15g) + 7 (5g) + 20 vol developer (60ml)
Time: 35-40 minutes
Expected result: Medium ash blonde without orange streaks

Common Mistakes and How to Avoid Them

1. Diagnosing by Eye

Problem: The perceived level isn’t the real one. Solution: Always use swatches and correct lighting.

2. Ignoring History

Problem: Unpredictable reactions with previous chemicals. Solution: Detailed file for each client.

3. Excess Corrector

Problem: Muddy or dull tones. Solution: Start with less, add if needed.

4. Not Doing Strand Tests

Problem: Unpleasant surprises at scale. Solution: Always test in doubtful cases.

5. Mixing Brands

Problem: Each system is internally calibrated. Solution: Use dye and developer from the same line.

Frequently Asked Questions

How many levels can dye lift?

Oxidative dye lifts a maximum of 4 levels on natural hair. For more lift, pre-lightening is required. This limit exists because dye deposits pigment while lightening, which limits its lifting power.

Why does orange appear when bleaching?

Orange is the underlying pigment of levels 5-6. It appears because when you remove melanin, the underlying pigments (pheomelanin) become visible. According to the International Association of Trichologists, this is a normal chemical process of hair, not a mistake. It’s neutralized with blue/ash.

What’s the difference between .1 and .01 in color codes?

The .1 indicates a pure, dominant ash. The .01 indicates a natural base with a soft ash undertone. The first is more powerful for neutralizing, the second is more natural and less cold.

Can I mix developers of different volumes?

Yes, to get intermediate volumes. The mix is proportional: 20 vol + 30 vol in equal parts = ~25 vol. But always from the same brand.

How long should I leave the dye on?

It depends on the goal: 30-35 minutes for standard color, 45 minutes for gray coverage. Never longer than the time indicated by the manufacturer. Extra time doesn’t improve the result, it only damages.

In Summary

Hair colorimetry is built on these pillars:

Color theory: Complementaries neutralize, primaries don’t mix to form pure colors
Level system: From 1 to 10, each level has its predictable underlying pigment
Reflects: The language of numbers after the decimal defines the final hue
Developers: The minimum necessary for the result, not the maximum available
Diagnosis: Without precise information, there’s no correct formulation

Mastering these fundamentals isn’t optional. It’s what allows you to go from “let’s see what happens” to “this is exactly what’s going to happen.”

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This article is the starting point of our colorimetry cluster. Explore the related articles to dive deeper into each specific topic.