Why does color mismatch occur?

Color mismatch is one of the problems frequently encountered in coating operations.

“The color differs from the reference panel.” “It looks slightly different from the previous lot.” “It was approved in Japan but looks different at the Vietnamese site.” “It was acceptable in the factory but rejected in the customer’s inspection room.”

When these problems occur, the paint is often the first thing suspected.

Is the paint from a different lot? Is the color match inaccurate? Is there a quality problem at the manufacturer?

Of course, the paint itself can be the cause. However, it is not the only possible cause of color mismatch.

The color of a coated product is not determined by the paint alone. Light strikes the coating film, which reflects and absorbs it. The reflected light reaches the human eye, and the brain perceives it as color.

Color is therefore perceived through a combination of the following factors.

• Paint
• Pigments
• Coating film
• Film thickness
• Underlying surface
• Gloss
• Light source
• Viewing angle
• Background
• Reference panel
• Human vision

If any of these changes, the color can appear different even when the same paint is used.

For this reason, a color mismatch complaint should not immediately be attributed to bad paint. The first question to establish is under what conditions the color looks different, and in what way.

Color is seen in the coating film, not in the paint can

Customers often refer to the color of a paint. From the perspective of coating technology, however, a more precise understanding is needed.

What the customer actually sees is not the liquid in the paint can. It is the coating film formed on the product surface.

Even with the same paint, the finished color can appear different if the following conditions change.

• Whether the film is thick or thin
• Whether the underlying color is light or dark
• Whether the number of coats is the same
• Whether the dilution ratio is the same
• Whether the drying conditions are the same
• Whether the gloss is the same
• Whether the surface texture is the same
• Whether mixing is sufficient
• Whether the application method is the same

For example, the underlying color can show through a thin film. A dark underlying surface can make the coating look darker, while a light one can make it look lighter.

A difference in gloss alone can also make colors appear different. A high-gloss surface reflects light strongly and may look brighter and more vivid. A matte surface scatters light and may appear more subdued.

Color is therefore the result of the coating film rather than a property of the paint alone.

Changing the light source changes color appearance

The light source is particularly important when assessing color mismatch.

The same coated product can look different depending on where it is viewed.

• In natural light
• Under LEDs inside the factory
• Under fluorescent lamps
• In the customer’s inspection room
• Outdoors in the evening
• In a dark warehouse

Each of these situations can change the appearance.

There are different types of light. Sunlight, LEDs, fluorescent lamps, and incandescent lamps contain different spectral components. Changing the lighting can therefore make the same coating film look redder, bluer, or darker.

Failing to understand this phenomenon can make color mismatch judgments inconsistent.

A product may be accepted in the factory but rejected at the customer’s site. The cause may be different lighting conditions rather than the paint.

When comparing colors, always check the following points.

• What lighting was used for the check?
• Were the reference panel and product viewed under the same lighting?
• Were they compared at the same angle?
• Were they viewed against the same background?
• Are natural light and artificial lighting being confused?
• What are the customer’s inspection conditions?

Color judgments are meaningful only when viewing conditions are consistent.

A reference panel cannot serve as a standard unless it is properly managed

Reference panels are important in color management.

A reference panel provides a common color standard for the customer, paint manufacturer, and coating factory. Simply having one, however, is not sufficient.

Reference panels themselves can change over time.

• They become dirty
• They become scratched
• They fade
• Their gloss changes
• They deteriorate because of storage conditions
• Differences develop between multiple reference panels
• Old and new reference panels are used together

In these conditions, the panels cannot function as a reliable standard.

Conditions for comparing the reference panel with production products are also important.

• Use the same light source
• Use the same viewing angle
• Use the same viewing distance
• Use the same background
• Compare at the same elapsed time after drying
• Check gloss differences as well
• Compare without dirt or scratches

Reference panels are more than objects to keep in storage. They must be maintained in a condition suitable for use as quality standards.

Color measurement values are useful but not sufficient on their own

Color measurement instruments may be used to assess color objectively.

Measured values allow color differences to be checked numerically in addition to visual inspection. This helps with customer quality confirmation and lot control.

However, measured color values are not a universal solution.

Measured color values are meaningful in conjunction with their measurement conditions.

Check the following conditions.

• Measuring instrument
• Measurement mode
• Light source conditions
• Observer conditions
• Measurement angle
• Measurement location
• Number of measurements
• Coating film thickness
• Gloss condition
• Underlying color
• Surface dirt or scratches
• Elapsed time after drying

Different measurement conditions make numerical comparisons difficult.

Colors can also seem wrong to the human eye even when their measured values are close. Conversely, a difference noticed visually may become smaller when lighting conditions are aligned.

Measured color values are therefore important, but quality decisions must not rely on numerical values alone.

What matters is combining visual inspection, reference panels, acceptance limit samples, measured color values, and measurement conditions.

A color on a screen is not the same as the color of a coated product

Customers increasingly specify colors using images or PDFs.

“Please match the color in this image.” “Please make it close to the color on this computer screen.” “Please use the color in this catalog.”

These specifications require care.

Smartphones, computer screens, printed materials, and actual coated products reproduce color in different ways.

Screens express color through light. Printing expresses color through ink. Coating expresses color through the coating film.

A color seen on a screen therefore cannot necessarily be reproduced perfectly with paint. Screen brightness settings and display types also change how colors appear.

The final choice of coating color must be confirmed using a physical coated sample.

In CoatureVietnam’s sales discussions, it is important to explain the following.

Colors in images or on screens can serve as references. However, the final confirmation of a production color must use a physical reference panel or coated sample.

This is very important for preventing subsequent problems.

Clarify what “the color is different” means

When a customer says that the color is different, accepting that wording without further clarification makes cause analysis difficult.

The phrase can describe several different issues.

One of the following may actually be occurring.

• Different hue
• Different lightness
• Different saturation
• Different gloss
• Different surface texture
• Different film thickness
• The underlying surface shows through
• Different lighting conditions
• Different reference panels
• Different viewing angles

For example, even when a customer says the color is deeper, it is necessary to determine whether it actually looks darker, more saturated, or glossier.

Breaking the complaint down into specific checks is the first step in addressing color mismatch.

Items to check when color mismatch occurs

The following sequence makes a color mismatch complaint easier to assess.

1. Is the comparison being made against a reference panel?

First, establish what is being compared when the color is judged different.

• The customer’s reference panel
• A previous lot
• Printed material
• An image on a screen
• An approved production sample
• A sample stored at the site

A sound judgment cannot be made while the comparison standard remains unclear.

2. Are the lighting conditions the same?

Check whether the reference panel and product are being compared under the same lighting.

• Natural light
• LED lighting
• Fluorescent lighting
• A standard light source in the inspection room
• Factory lighting

Different light sources change color appearance.

3. Is the film thickness the same?

Different film thicknesses can change color appearance.

Differences in thickness can cause color differences, particularly for colors with insufficient hiding power or strong sensitivity to the underlying surface.

Check the following items.

• Specified film thickness
• Measured film thickness
• Variation in film thickness
• Presence of thin-film areas
• Film thickness at corners and edges
• Whether the underlying surface shows through

4. Are the underlying surface conditions the same?

Differences in the underlying color or surface preparation conditions change how the topcoat looks.

Check the following items.

• Is the substrate the same?
• Is the primer the same?
• Are the surface preparation conditions the same?
• Is the underlying color the same?
• Is the surface roughness the same?
• Has sanding or repair been performed?

Even with the same topcoat, a different underlying surface changes the finish.

5. Is the gloss the same?

A difference in gloss can be perceived as a color difference.

Gloss and matte finishes can give very different impressions even with the same color. Higher gloss can make the color look brighter or deeper. Lower gloss can make it look more subdued or whitish.

Check the following items.

• Is gloss specified?
• Is gloss checked with a gloss meter?
• Is there uneven gloss?
• Are the drying conditions the same?
• Is the coating film’s surface texture the same?

6. Are the paint conditions the same?

Paint-related conditions also need to be checked.

• Paint lot
• Color-matching lot
• Dilution ratio
• Thinner used
• Mixing condition
• Storage condition
• Pot life
• Hardener mixing ratio
• Paint temperature
• Filter use

Insufficient mixing or different dilution ratios can cause uneven color or gloss.

7. Are the drying and baking conditions the same?

Different drying or baking conditions can change gloss and color tone.

Check the following items.

• Drying temperature
• Drying time
• Baking temperature
• Baking time
• Heating profile
• Uneven oven temperature
• Elapsed time after drying

Differences in drying and curing conditions can affect appearance, particularly with baking paints and two-component reactive paints.

Color management through the 4Ms plus Management

CoatureVietnam organizes color mismatch issues using the 4Ms plus Management.

Material: materials

For materials, check the following items.

• Paint lot
• Pigment dispersion
• Color-matching accuracy
• Dilution ratio
• Thinner used
• Hardener
• Primer
• Underlying color
• Reference panel
• Acceptance limit samples

Color management must include the underlying surface and reference panels as well as the paint.

Method: methods

For methods, check application conditions and inspection conditions.

• Number of coats
• Film thickness
• Spray conditions
• Drying conditions
• Color checking method
• Inspection distance
• Inspection angle
• Lighting conditions
• Color measurement conditions

It is important to standardize both how the paint is applied and how the color is viewed.

Machine: equipment

For equipment, check application equipment and the inspection environment.

• Spray gun
• Paint supply equipment
• Mixer
• Drying oven
• Standard light source
• Color measurement instrument
• Gloss meter
• Film thickness gauge
• Inspection table
• Factory lighting

Inspection equipment is important in color management as well as coating equipment.

Man: people

Human judgment is also a major factor in color management.

• Operator application skills
• Inspectors’ visual judgment
• Sales representatives’ ability to gather information
• Quality personnel’s assessment skills
• Agreement with the customer
• Initial response to color mismatch

Human perception does not need to be dismissed. However, it needs support from standards and conditions rather than being the sole basis for decisions.

Management: management

Management requires a system that treats color as a quality characteristic.

• Reference panel storage
• Management of acceptance limit samples
• Recording measured color values
• Management of customer-approved samples
• Recording application conditions
• Standardizing inspection conditions
• Maintaining color mismatch histories
• Aligning customer and internal standards

Color management is not solely a production-site issue. Sales, quality, manufacturing, and customers need to discuss it using the same standards.

Color management challenges likely to arise in Vietnamese factories

The following challenges are considered likely in Vietnamese factories.

• Color judgments depend on individuals’ visual assessments
• Reference panels are inadequately managed
• Lighting is not consistent between inspection locations
• Natural light and factory lighting are confused
• Color measurement values are available, but measurement conditions are not recorded
• Gloss differences are treated as color differences
• Film thickness control is inadequate
• Differences in underlying surface conditions are not checked
• Customer and internal acceptance criteria differ
• Colors in images or PDFs are used directly as coating color standards

These challenges are not caused solely by a lack of color knowledge. They arise because a system for managing color has not been established.

Practical steps to prevent color mismatch

Establishing the system in the following order is effective for preventing color mismatch.

Step 1: Define the standards

First, decide what constitutes the reference color.

• Customer reference panel
• Approved sample
• Acceptance limit samples
• Measured color values
• Gloss standard
• Film thickness standard

Color management cannot begin while the standards remain unclear.

Step 2: Align checking conditions

Standardize the conditions under which color is viewed.

• Inspection location
• Lighting conditions
• Inspection angle
• Inspection distance
• Background color
• Measurement conditions
• Timing of the check after drying

Comparison under the same conditions is fundamental to color judgment.

Step 3: Control application conditions

Stable color requires application conditions to be controlled.

• Dilution ratio
• Viscosity
• Mixing
• Film thickness
• Number of coats
• Drying conditions
• Underlying surface conditions
• Application method

Color management is process control as well as inspection.

Step 4: Keep records

Records are important for preventing color mismatch problems.

• Paint lot used
• Dilution conditions
• Film thickness
• Drying conditions
• Measured color values
• Inspection results
• Reference panel number
• Customer approval history

Records make it easier to trace causes when a problem occurs.

Step 5: Share acceptance criteria with the customer

Finally, agreement with the customer is necessary.

A product accepted internally may be rejected by the customer. The reason may be different assessment conditions or tolerances rather than the color itself.

It is therefore important to share the following with the customer.

• Reference panel
• Acceptance limit samples
• Color measurement conditions
• Permissible color difference
• Gloss standard
• Light source for assessment
• Inspection conditions
• Approved production sample

The goal of color management is to enable judgments using the same standards as the customer.

Color management knowledge is also necessary for sales

Color management is not solely the job of quality and technical departments. Sales representatives also need this knowledge.

If a salesperson simply apologizes and passes a customer’s color complaint to the manufacturer, the underlying problem will remain difficult to identify.

The quality of the initial response improves substantially when sales representatives can ask questions such as the following.

• What did you compare it with when it looked different?
• What lighting did you use to check it?
• Did you compare the reference panel and product under the same conditions?
• Is the difference in hue or lightness?
• Is there a difference in gloss?
• Do you have film thickness data?
• Are the underlying surface conditions the same?
• Are the drying conditions the same?
• Do you have measured color values?

Sales representatives who can make these checks gain trust as people who understand coating processes, rather than simply selling paint.

How CoatureVietnam can help

CoatureVietnam investigates the whole process when addressing color mismatch, rather than examining the paint alone.

We can provide the following support.

• Initial analysis of color mismatch causes
• Support for using reference panels and acceptance limit samples
• Defining color measurement conditions
• Checking film thickness, gloss, and underlying surface conditions
• Standardizing inspection conditions
• Creating color management SOPs
• Training sales teams to gather relevant information
• Training quality personnel in appearance assessment
• Checking application conditions
• Aligning customer and internal standards
• Support to prevent recurring color mismatch complaints

Color mismatch is not necessarily a paint problem alone. Materials, methods, equipment, people, and management therefore need to be assessed together.

Summary

The color of a coated product is not determined by the paint alone.

Color appearance changes with light, the coating film, film thickness, the underlying surface, gloss, lighting, viewing angle, reference panels, and human vision.

To prevent color mismatch complaints, establish the following standards rather than relying solely on perception.

• Reference panel
• Acceptance limit samples
• Measured color values
• Lighting conditions
• Film thickness
• Gloss
• Underlying surface conditions
• Drying conditions
• Inspection method
• Acceptance criteria agreed with the customer

Color management is more than color matching. It is process control that stabilizes coating quality and protects customer trust.

The following perspective is important.

Color mismatch is not just a paint problem. Color is determined by the coating film, light, and the viewing environment. Color therefore needs to be managed through conditions and standards rather than perception alone.