Color codes and color names are commonly used to specify coating colors.

Munsell notation.
JPMA color codes.
Manufacturer color codes.
Customer-specified colors.
Color names on drawings.
Colors shown in PDFs or printed material.
Colors sent in photographs.

These are necessary information for communicating color.
However, proceeding with mass-production coating based only on a color code or printed material is risky.

This is because a coating color is not completely determined by its code alone.

Even with the same color code, the actual appearance may vary with the coating manufacturer, material batch, coating method, film thickness, underlying surface, drying conditions, gloss and lighting.

To achieve consistent coating color, it is therefore important to use more than just a color code and to agree with the customer on an actual coated sample panel made with the coating material that will be used as the reference.

1. A color code is a starting point for color agreement, not the final criterion

Color codes are convenient.
They provide a shared identifier for customers, design, purchasing, coating manufacturers and the shop floor to discuss the same color.

However, a color code is only a starting point.

In actual coating, appearance can vary with the following conditions even when the color code is the same.

• Coating manufacturer
• Pigment type
• Coating material batch
• Coating method
• Film thickness
• Underlying color
• Drying conditions
• Baking temperature
• Gloss
• Surface texture
• Lighting
• Viewing angle
• The viewer’s perception

Thus, the same color code does not necessarily mean that a customer will see the same color.

A color code is a starting point for finding a color.
However, it is insufficient as the final criterion for assuring production quality.

Ultimately, an actual coated sample panel must be used to check the color as a real coating film.

2. Do not use printed material or PDF colors as the acceptance reference

Customers sometimes specify colors using printed material, PDFs, photographs or screenshots.

Such documents help communicate a color concept.
However, they cannot be used directly as coating color acceptance criteria.

This is because printed material and coating films produce color differently.

Printed material represents color through ink.
Screens represent color through light.
Coatings represent color through a film containing pigments.

Furthermore, printed colors vary with paper quality and printing conditions.
The appearance of PDFs and photographs varies with monitors, smartphones, cameras and lighting.

Therefore, even when a customer points to printed material or a PDF and requests that color, the coating material may not be able to reproduce it exactly.

Particular care is needed with vivid reds, yellows, purples, metallic effects and colors with special textures.
Colors that can be represented in print or on a screen may be difficult to reproduce with industrial coating materials.

Printed material and PDFs are only reference information.
The standard for production coating should always be checked using an actual coated sample panel.

3. What is an actual coated sample panel?

It is a panel for checking color, made with the coating material to be used and a method close to the actual coating conditions.

It differs from a simple color chip or printed sample.

An actual coated sample panel allows the following information to be checked.

• Actual color
• Gloss
• Film surface texture
• Appearance at the relevant film thickness
• Influence of the underlying surface
• Color changes caused by drying conditions
• Characteristics of the coating material batch
• The impression actually seen by the customer

To agree coating color correctly, this actual coated sample panel needs to be shared among the customer, the coating shop floor, quality assurance and the coating manufacturer.

For parts where appearance quality is important in particular, entering mass production without an actual coated sample panel creates a major risk.

4. Sample panels should be made under the same conditions as mass production

There is an important point to remember when making a sample panel.

It should be made under conditions as close as possible to mass production.

For example, if mass production uses spray coating but the sample is made by brushing, the finish may differ from actual production.
If mass production uses baking but only the sample is air-dried, color or gloss may differ.
If mass production coats steel but the sample uses a different substrate, the influence of the underlying surface may differ.

At least the following conditions should be recorded when making a sample panel.

• Coating material used
• Coating material batch
• Thinner used
• Thinning ratio
• Coating method
• Film thickness
• Substrate
• Underlying surface preparation
• Drying conditions
• Gloss
• Date made
• Approver

Simply making a sample panel is not enough.
It can be used as a production reference only when the conditions under which it was made are recorded.

5. Agree gloss as well as color

Color matching tends to focus on the color itself.
In practice, however, gloss is also very important.

Even with the same color, full gloss, semi-gloss and matte finishes look substantially different.
A gloss difference alone can make a color look deeper, paler, lighter or duller.

When checking a color sample panel, gloss therefore needs to be checked as well as color.

The following items should be agreed with the customer.

• Color
• Gloss
• Surface texture
• Acceptable color difference
• Acceptable gloss difference
• Viewing conditions
• Acceptance range

Even when the color code matches, different gloss may make the customer see a different color.

Color and gloss should be agreed together as appearance quality, rather than considered separately.

6. Acceptance-limit samples make shop-floor judgments more consistent

A standard sample panel shows the target color.
However, it may be difficult to reproduce exactly the same color every time in mass production.

Creating acceptance-limit samples where necessary is therefore useful.

Acceptance-limit samples show the upper and lower limits of the acceptable range.
For example, they physically show the boundary between “acceptable up to this level” and “unacceptable beyond this difference.”

Acceptance-limit samples make shop-floor judgments more consistent.

Operators, inspectors and customers can more readily judge against the same criteria.
Subjective discussions are reduced, as are unnecessary rework and recoating.

Acceptance-limit samples are particularly useful for the following products.

• Parts with important appearance requirements
• Products with demanding customer requirements for color difference
• Products prone to color variation between batches
• Products with a history of color-difference complaints
• Products made in multiple factories or by multiple subcontractors

Acceptance-limit samples are highly practical quality references for the shop floor.

7. Agree the acceptable color-difference range with the customer

A color-difference meter is sometimes used for numerical color-difference control.

A color-difference meter is convenient.
However, decisions should not be based on numbers alone.

The same numerical color difference may create a different visual impression.
Appearance also changes with hue, lightness, chroma, gloss and surface texture.

The following items therefore need to be agreed with the customer for color-difference control.

• Whether to measure color differences or judge them visually
• The measurement method when using a color-difference meter
• Measurement locations
• Number of measurements
• Tolerance
• Light source conditions
• Viewing distance
• How to judge a disagreement between visual assessment and numerical values

A tighter color-difference tolerance is not necessarily better.
It is important to set a range suited to the product’s application.

Appearance parts viewed at close range require strict control.
For internal or structural parts, however, excessive color control may be unnecessary.

What matters is agreement with the customer in advance.
Criteria need to be shared to avoid later comments that the color is different from what was expected.

8. Color samples require management after they are made

Color sample panels are not finished with once they have been made and approved.

Sample panels may change over time.
Light, heat, humidity, contamination and storage conditions can change their color or gloss.

Continuing to use old sample panels may cause the reference itself to drift.

Color sample panels therefore need to be managed.

Manage the following items.

• Date made
• Approval date
• Approver
• Coating material used
• Coating material batch
• Storage location
• Expiration date or renewal timing
• Handling method
• Renewal history
• Comparison records with the previous sample

Color sample panels are important references for quality assurance.
If a reference deteriorates, judgments also shift.

For coating supplied to Japanese manufacturers in particular, it is important to properly manage sample storage, renewal and approval history.

9. Alternative coatings need care even with the same color code

Vietnamese factories sometimes consider alternative coatings because of costs, delivery times, local procurement, import restrictions or other reasons.

In this situation, it is risky to conclude that the alternative is acceptable merely because its color code is the same.

Even with the same color code, a change of manufacturer may change pigments, resin, gloss, hiding power and drying characteristics.
The color may also look different under a different light source.

When considering alternative coatings, the following checks are needed.

• Compare actual coated sample panels
• Check using the same coating method as mass production
• Align film thickness
• Align drying conditions
• Check gloss
• Check under multiple light sources
• Obtain customer approval
• Agree the acceptable color-difference range

Evaluating an alternative coating requires checking the actual film, not only the color code.

10. Color specification problems commonly encountered in Vietnamese factories

The following color specification problems may commonly occur in Vietnamese factories.

• The Japanese headquarters specifies the color only through a PDF
• The customer specifies the color only through a photograph
• The drawing gives only a color code
• There is no actual coated sample panel
• The color sample panel is old
• The panel’s approval history is not retained
• Factory lighting differs from lighting in the customer’s inspection room
• Standard samples are not shared with subcontractors
• Alternative coatings are judged only by their color codes
• The acceptable color-difference range has not been set

Starting mass production under these conditions may lead to color-difference complaints later.

Resolving a color problem after it occurs can be costly.
It can involve recoating, sorting, disposal, delivery delays and customer response.

That is why agreement using actual coated sample panels before mass production is important.

11. Organize color agreement through 4M

Organizing color agreement through 4M makes it easier to apply in practice.

Material: Materials

Check coating materials, pigments, thinner, substrate material and coating batches.

• Which coating material is used?
• Who is the coating manufacturer?
• Is the coating material batch recorded?
• Are there pigment or gloss differences?
• For an alternative coating, has equivalence been checked?

Method: Methods

Check how sample panels are made, coating methods, drying conditions and measurement methods.

• Was the sample panel made using the same method as mass production?
• Is film thickness aligned?
• Are drying conditions the same as mass production?
• Has the color-difference measurement method been set?
• Have visual assessment conditions been set?

Machine: Equipment

Check coating equipment, drying ovens, lighting and color measurement instruments.

• Are there differences between sample-making and mass-production equipment?
• Are drying oven conditions stable?
• Is inspection lighting consistent?
• Is the color-difference meter managed?

Man: People

Check the judgment criteria of inspectors, operators and approvers.

• Who approves the color?
• Who keeps the sample panels?
• Are inspectors’ judgment criteria consistent?
• Can operators check the standard samples?

12. Management perspective: Standardize the color approval process

Standardizing the color approval process is important for preventing color-difference complaints.

For example, the following flow is useful.

1. Check the customer’s required color
2. Obtain the color code, drawings and reference information
3. Check feasibility with the coating manufacturer
4. Make an actual coated sample panel
5. Obtain customer approval
6. Manage standard sample panels and acceptance-limit samples
7. Check the first production products
8. Recheck when the batch changes
9. Renew sample panels regularly

If this flow remains unclear, both responsibilities and judgment criteria will be unclear when a color problem occurs.

Color approval is a management task involving sales, quality assurance, production engineering, purchasing, the coating shop floor and the coating manufacturer.

It is important to manage it through a process rather than intuition.

13. Coating the Future with Science and Care

The purpose of color management is not to make everything more detailed and strict.

What matters is creating criteria that give customers confidence, remove uncertainty for the shop floor and allow fair judgments by quality assurance.

An actual coated sample panel allows operators to check the target.
Acceptance-limit samples make inspectors’ judgments easier.
A color-difference tolerance reduces misunderstandings with customers.
Managed sample panels allow consistent judgments when batches change or products are made again.

This directly connects to CoatureVietnam’s principle, “Coating the Future with Science and Care.”

Science means managing color through sample panels, film thickness, gloss, lighting and measurement conditions, rather than perception alone.
Care means using that management to help operators and inspectors make decisions without uncertainty.

Agree color using an actual coated sample panel, rather than relying on the color code alone.
That is the first step in preventing color-difference complaints.

Practical checklist

When specifying or managing coating colors, check the following.

• Are you starting mass production based only on a color code?
• Is there an actual coated sample panel?
• Was it made using the same coating method as mass production?
• Are the sample’s film thickness, drying conditions and coating material batch recorded?
• Is the customer approval history retained?
• Have gloss and color both been agreed?
• Are there acceptance-limit samples?
• Has the acceptable color-difference range been set?
• Are lighting conditions for visual assessment consistent?
• If a color-difference meter is used, has the measurement method been set?
• Are there rules for storing and renewing sample panels?
• When using an alternative coating, is it checked through actual coating?
• Are the same sample panels shared with subcontractors?

CoatureVietnam’s perspective

Preventing color-difference complaints requires checking color as an actual coating film, rather than only through a color code.

CoatureVietnam supports color management in Vietnamese factories through actual coated sample panels, color-difference checks, alternative coating evaluation and clarification of customer approval processes.

Managing color by perception alone creates problems.
With sample panels, tolerances, lighting conditions and approval histories in place, color management becomes a quality reference that can be used on the shop floor.