EPO Allows Colour Drawings: What Patent Applicants Need to Know in 2026

EPO Allows Colour Drawings: What Patent Applicants Need to Know in 2026

For many years, patent applicants preparing European patent applications generally had to rely on black-and-white drawings. While colour could sometimes make a technical illustration easier to understand, traditional EPO practice meant that colour drawings were converted to black and white during processing.

That changed on October 1, 2025.

The European Patent Office (EPO) introduced electronic filing and processing of colour and greyscale drawings, allowing them to retain their original appearance throughout the digital patent-granting process. This is an important development for applicants whose inventions are easier to understand when different components, materials, layers, surfaces, or technical features are visually distinguished.

For patent applicants preparing applications in 2026, however, there are still important requirements and limitations to understand.

Does the EPO Now Allow Colour Patent Drawings?

Yes. Since October 1, 2025, colour and greyscale drawings are permitted for European patent applications when they are filed electronically.

The EPO's current 2026 Guidelines confirm that drawings may be submitted in colour or greyscale provided they are filed electronically. Black-and-white drawings remain fully acceptable as well.

This means applicants no longer have to automatically convert every patent drawing to black and white simply because the application is being filed with the EPO.

The change is particularly useful for inventions where colour communicates technical information more effectively than line drawings alone.

For example, colour may help distinguish different materials in a composite structure, identify separate layers in an electronic device, illustrate fluid paths, show different components in a complex assembly, or make certain medical and biological structures easier to interpret.

What Changed on October 1, 2025?

Before the change, colour drawings submitted to the EPO were generally processed into black and white. The EPO's new system provides end-to-end support for colour and greyscale drawings.

According to the EPO, electronically filed colour and greyscale drawings can now retain their characteristics throughout the digital patent-granting process instead of being automatically converted into black and white. They can also appear in colour or greyscale in relevant EPO publications and file inspection systems.

This is more than a cosmetic change. It means that the visual information contained in a properly prepared colour drawing can remain available to examiners and the public in the format originally filed.

The change also reflects the EPO's broader move toward end-to-end electronic processing of patent applications.

What Are the Technical Requirements?

The fact that colour drawings are now accepted does not mean that applicants can submit any type of coloured image.

The EPO still expects patent drawings to meet its formal requirements.

Under the current rules, electronically filed colour or greyscale drawings must use durable, uniformly thick and well-defined lines, strokes or areas. They must also provide sufficient contrast and be suitable for clear display at a resolution of 300 dpi.

This is important when preparing drawings for filing.

A drawing that looks attractive on a high-resolution monitor may not necessarily be suitable for a patent application. Very light colours, low-contrast shading, excessive gradients, or unclear boundaries can make technical features difficult to identify.

The objective should therefore be clarity rather than decoration.

A professional patent illustrator should consider how the drawing will appear after electronic processing and publication, not just how it looks in the original design software.

Can Colour and Black-and-White Drawings Be Used Together?

Yes.

The EPO permits mixed submissions containing colour, greyscale and black-and-white drawings.

This gives applicants some flexibility.

For example, an application might use conventional black-and-white line drawings for mechanical components while using colour for a particular figure where colour provides meaningful technical information.

However, consistency is still important. Figures should have a coherent visual style, numbering system, reference characters and overall presentation.

Using colour simply because it is available is not necessarily a good idea. If black-and-white adequately communicates the invention, it may still be the better choice.

When Is Colour Particularly Useful?

Colour can be valuable when it communicates information that would otherwise be difficult to distinguish.

Some examples include:

• Different layers within a semiconductor or electronic structure

• Multiple materials within a composite product

• Fluid or gas flow paths

• Different components within a complex mechanical assembly

• Medical or biological structures

• Spatial relationships between components

• Different regions or sections of a technical system

• Before-and-after or comparative technical conditions

For instance, imagine a technical drawing showing several internal layers of a device. If all layers are represented with identical line patterns, the reader may need to study the figure carefully to understand the structure. Carefully selected colours can make the different layers immediately distinguishable.

The key is that colour should support technical understanding.

Do Not Rely on Colour Alone

One important point applicants should remember is that colour should not necessarily be the only way a feature is identified.

The EPO advises applicants not to refer to colour-specific features in the description, claims or abstract, such as describing a component as "yellow" or "beige," because colour specifications may not always be reliably and objectively identifiable.

This is an important drafting consideration.

Instead of making the technical meaning of an element dependent entirely on its colour, the drawing should use appropriate reference numbers, labels, line work and other conventional drafting techniques.

Colour should enhance the illustration rather than become the sole means of understanding the invention.

What About PCT Applications?

This is one of the most important distinctions.

The EPO's new colour-drawing practice does not change the PCT international-phase rules.

Colour drawings are still not admissible under the PCT rules. Where colour drawings are included in an international application, the International Bureau may render them in black and white for international processing and publication. However, electronically filed colour or greyscale versions may also be retained by WIPO and made available through PATENTSCOPE under the applicable procedure.

Therefore, applicants should not assume that because the EPO accepts colour drawings, every patent office or every stage of an international application will treat them in the same way.

This distinction becomes particularly relevant for Euro-PCT applications entering the European regional phase.

For Euro-PCT applications entering the European phase on or after October 1, 2025, the EPO can process colour or greyscale drawings where the relevant colour version is available on PATENTSCOPE and the international publication indicates that the original application contained colour or greyscale drawings.

What About Priority Applications?

Applicants also need to be careful when claiming priority.

The EPO's notice specifically addresses situations involving missing or corrected drawings and priority documents. For example, if the drawings in the priority application were filed in black and white, replacing them later with colour drawings can raise issues because the later drawings must correspond appropriately to the earlier disclosure.

This is another reason why applicants should not treat the ability to file colour drawings as simply a formatting choice.

Changes to drawings can have legal consequences under the EPC, including requirements concerning added subject matter and priority.

What Does This Mean for Patent Applicants in 2026?

The EPO's new practice provides applicants with greater flexibility when preparing patent illustrations.

Colour can be especially helpful for technically complex inventions where visual differentiation improves understanding. At the same time, applicants should continue to focus on accuracy, consistency and compliance with EPO requirements.

A good patent drawing is not simply an attractive technical illustration. It is part of the patent application and needs to communicate the invention clearly and accurately.

Applicants should therefore consider several questions before choosing colour:

Does colour communicate useful technical information?

Will the important features remain clear at 300 dpi?

Are the colours sufficiently contrasting?

Could the invention still be understood if colour were removed?

Are the drawings consistent with the description and claims?

Are there priority or PCT considerations that need to be addressed?

Answering these questions can help avoid unnecessary problems later.

The Role of Professional Patent Drawing Services

The EPO's acceptance of colour drawings gives patent applicants more options, but it also places greater importance on preparing drawings correctly.

Professional patent illustrators can help convert technical sketches, CAD models, photographs or inventor concepts into clear patent-ready figures while maintaining consistent line work, reference numbers, proportions and figure formatting.

For applicants filing in Europe, it is also important that the drawing team understands the difference between EPO, USPTO and PCT requirements. A drawing prepared for one jurisdiction should not automatically be assumed to satisfy another jurisdiction's rules.

At Patent Render, our focus is on producing accurate, professional patent illustrations designed around the requirements of the relevant patent office. Whether an application requires traditional black-and-white line drawings or carefully prepared colour and greyscale figures, the goal remains the same: to present the invention clearly and professionally.

Conclusion

The EPO's acceptance of electronically filed colour and greyscale drawings represents a significant modernization of European patent filing practice.

Since October 1, 2025, eligible European patent applications can include colour and greyscale drawings that remain in their original format through the EPO's digital patent-granting process. The 2026 EPO Guidelines now reflect this change.

However, colour should be used thoughtfully. Applicants still need to meet technical requirements, maintain sufficient contrast and consider issues involving priority, amendments and PCT applications.

Ultimately, the purpose of a patent drawing is not to make an application look more colourful. Its purpose is to communicate the invention accurately, clearly and consistently.

When colour genuinely improves that communication, the EPO's updated practice gives applicants an additional tool for presenting their inventions effectively.