Why Colour Contrast is Important for Digital Accessibility

What is colour contrast?

Colour contrast is the term given to describe the difference in relative brightness between an element and the colour behind or beside it.

One example, and one of the most common issues, is text on a background. Black text on a white background has very high contrast. Light grey text on a white background has much lower contrast and may be difficult to read.

Beyond text, there are other elements that could also affect contrast to the user. Here are some of them:

1. Buttons and their boundaries
2. Form fields and input borders
3. Icons and meaningful graphics
4. Links within surrounding text
5. Focus indicators used during keyboard navigation
6. Selected, checked, expanded and error states
7. Charts, diagrams and data visualisations

A design can look attractive and consistent with a brand while still having insufficient colour contrast. That is why it’s not enough to determine if the design works using visual judgement alone. Colour contrast needs to be measured to make sure it included all users.

Who benefits from sufficient colour contrast?

People with low vision are normally the ones who get directly affected by insufficient colour contrast. Text or controls that looks clear to one person may be faint or indistinguishable to somebody with reduced vision or contrast sensitivity.

People with colour vision deficiency may also find particular colour combinations difficult to distinguish. This is especially important when a design relies on differences between colours to communicate meaning.

For example, when green is used to show something positive, and red to something negative, users with low vision may find it difficult to understand what you’re communicating, especially if colour is the only way your format chosen to present this message.

Contrast sensitivity can also change as people age. A colour combination that appears clear to a younger designer may be considerably harder for an older user to see.

The benefits are not limited to people with permanent disabilities. Content with good colour contrast can help users:

• Using a phone in bright sunlight

• Viewing a screen with glare or reduced brightness

• Using an older or lower-quality display

• Experiencing eye strain or fatigue

• Recovering from an eye injury or medical procedure

• Working in an environment where a screen is difficult to see

Good colour contrast makes designs more accessible and easier to use in different situations.

Why colour contrast matters to digital accessibility

Digital accessibility means ensuring that websites, applications and digital content can be used by people with different abilities and access needs.

For sighted users, the ability to distinguish content from its background is essential. If someone cannot read the text, identify an input or locate the next action, the experience is surely not accessible to them.

Poor colour contrast can create barriers at every stage of a digital journey.

A customer may struggle to read product information, identify a price, complete a form or recognise a checkout button. A student may miss important guidance in an online course. An employee may be unable to interpret a dashboard or locate a required control.

These are not minor problems. They can prevent people from accessing information or completing tasks. When user experience is compromised, your conversion rate is too.

One important statistic to demonstrate this scenario is the 2026 review of the world’s top one million home pages made by WebAIM. It found low-contrast text on 83.9% of them. It was the most common accessibility issue detected.

What does WCAG require for colour contrast?

The Web Content Accessibility Guidelines, known as WCAG, provide internationally recognised requirements for digital accessibility, including colour contrast.

For WCAG 2.2 Level AA, the minimum contrast requirements for text are:

• Normal text: a contrast ratio of at least 4.5:1

• Large text: a contrast ratio of at least 3:1

Large text generally means at least 18 point, or at least 14 point when bold. The W3C provides further detail in its guidance for WCAG Success Criterion 1.4.3: Contrast (Minimum).

For the enhanced Level AAA requirement, the thresholds increase to:

• Normal text: at least 7:1

• Large text: at least 4.5:1

The ratio should not be rounded up. A result of 4.49:1 does not meet a 4.5:1 requirement.

Logos and purely decorative or incidental text have specific exceptions. However, these exceptions should not be used to justify faint text or controls that people need to understand or operate.

Contrast applies to more than text

One of the most common misunderstandings is that colour contrast only applies to words.

Under WCAG Success Criterion 1.4.11: Non-text Contrast, visual information needed to identify user-interface components and their states generally needs a contrast ratio of at least 3:1 against adjacent colours.

This can include the visible border of a form field, an icon required to understand an action, the selected state of a control or the indicator showing where keyboard focus is located.

If a button has clear text but its boundary disappears into the surrounding background, some users may not recognise it as a button. If an input field has no visible outline, people may not know where to enter information. If the keyboard focus indicator is too faint, a keyboard user may lose track of their position on the page.

Testing the contrast of text alone does not provide the complete picture.

Colour must not be the only way meaning is communicated

Sufficient contrast and the use of colour are related, but they are not the same requirement.

WCAG Success Criterion 1.4.1: Use of Color states that colour should not be the only visual way of conveying information, indicating an action, prompting a response or distinguishing an element.

For example, consider a form that shows an invalid field only by changing its border from grey to red. A person who cannot distinguish those colours may not know that anything has changed.

A more accessible design could use:

• A clear text error message

• An error icon as well as a colour change

• A descriptive label identifying the problem

• A pattern, shape or line style in addition to colour

The same principle applies to charts and dashboards. If categories are distinguished only by colour, provide labels, patterns or symbols as well.

The aim is not to stop designers using colour. Colour is still valuable. But to make sure that all users can understand the information, adding more than one format to comprehend it is the best solution.

Common colour contrast problems

As you’ve seen in the latest WebAIM report, colour contrast issues are the most common problems in websites. Some failures appear repeatedly across pages and digital products. Here are some of them:

Light grey body text

Grey text can create a softer visual style, but very light grey against white often fails minimum contrast requirements. Body text, supporting instructions and prices still need to remain readable.

Text placed over images

The background behind the text may change across an image. A combination that passes over one area may fail over another. Overlays, solid text backgrounds or carefully controlled image areas can provide more reliable contrast.

Brand colours used without adjustment

A brand colour may work well for decorative elements but fail when used for small text or controls. Accessible design does not require abandoning the brand style. It may require darker or lighter functional variants for particular uses.

Placeholder text used as a label

Placeholder text is frequently low contrast and disappears when someone begins typing. It should not replace a persistent, properly associated form label.

Faint form-field borders

An input with a very light border can merge into the background. Test the visual information people need to recognise the control, not only the text inside it.

Inaccessible interaction states

Hover, focus, selected, checked and error states may introduce new colour combinations. Every meaningful state needs to remain perceivable.

Information shown through red and green alone

Using green for success and red for failure is common, but colour alone is insufficient. Add text, icons or another visible distinction.

How to test colour contrast

So now that you know what it is, its importance, and the most common issues around colour contrast, it’s time to understand how to test that your selected colours are accessible, with proper contrast ratio between them.

Contrast should be checked during design, development, content creation and ongoing quality assurance. A practical process is:

1. Identify foreground and background colours for text, controls and meaningful graphics.
2. Use a contrast-checking tool to calculate the ratio.
3. Test normal, hover, focus, selected, disabled and error states where relevant.
4. Check text placed over gradients, images and video at its least contrasting point.
5. Review whether colour is being used as the only way to communicate meaning.
6. Test at different screen sizes and zoom levels.
7. Include disabled users and accessibility specialists in broader usability testing.

One of the best ways for testing is using an automated scanning tool. They can identify many contrast failures quickly and consistently. The Nexus Inclusion Free Webpage Contrast Checker can help teams detect low-contrast combinations across a webpage and understand where improvements are required.

For users doing a manual audit to calculate, our Free Contrast Checker Browser Extension is a great tool to analyse the website based on a human review, which is good for accessibility experts.

Start with a free check, then examine the complete experience

If you are not sure where your website stands, begin with the Nexus Inclusion Free Website Accessibility Checker. It checks a homepage against WCAG 2.2 Level AA and gives you an initial view of barriers, including colour contrast issues. It’s free, no account or card needed to start.

That first result is a starting point, so you know how accessible your homepage is at the moment. A homepage cannot represent every template, component, user journey or interaction state across a website. The next step is to investigate the wider experience:

• Use the Website Accessibility Scanner to test the pages and journeys that matter, including forms, product pages, checkout or booking steps and account areas.

• Use the Webpage Contrast Checker to analyse text, backgrounds and interface elements across a complete page, rather than checking isolated colour pairs alone.

• Use Image Analysis to examine visual content for accessibility issues, including images and text overlays that may be difficult for some people to perceive or understand.

• Combine automated results with human review to check focus indicators, hover and error states, colour-only meaning and the real experience of completing a task.

Following the steps above will help you create a practical progression:

1. Understand the barriers
2. Analyse where and why they occur
3. Fix the design or content
4. Retest the experience

Once the immediate issues have been addressed, turn on accessibility monitoring so that new content and component changes do not reintroduce colour contrast failures already handled by your team.

While colour contrast is an important part of this journey, it is not the whole of inclusion.

Nexus Inclusion’s platform also provides advanced tools for keyboard tabbing order, page structure and content. Used together, these checks help teams move from finding isolated accessibility failures towards creating digital experiences that more people can understand, navigate and use.

The best part is that you can access all these tools in one place. Our tool works on detection, analyses, guidance, and monitoring.

How to improve colour contrast without losing your brand

Accessibility and brand design do not need to compete. They should complete each other.

Start by defining accessible colour combinations within the design system. Document which colours can be used together for body text, headings, buttons, links, form controls and interaction states.

If an existing brand colour does not provide sufficient contrast, consider:

1. Creating a darker or lighter accessible variant
2. Changing the text colour while retaining the background
3. Using the brand colour for larger decorative areas instead of small text
4. Adding a border, fill or underline where it improves recognition
5. Increasing contrast without changing the overall hue more than necessary
6. Providing more than one visual cue for states and messages

When using our Colour Contrast Checker, you’ll find not only where your page has failures, but also suggestions of better colour combinations that would work better in your design.

These decisions are easier and less expensive when they are made at design-system level. A corrected component can improve every page where it is used.

Colour contrast needs ongoing attention

A website can meet contrast requirements today and develop new failures tomorrow.

New campaigns, images, templates, components and brand updates can all introduce inaccessible combinations. Third-party widgets and content-management changes can also affect how colours appear.

That is why colour contrast should be included in regular accessibility monitoring. Ongoing checking helps teams identify regressions early and maintain a consistent standard as the product changes.

Good contrast makes digital experiences clearer

Colour contrast is one of the most visible and measurable areas of digital accessibility, but its importance goes beyond passing a test.

Good colour contrast makes content easier to read. It makes controls easier to recognise. It helps people understand states, errors and actions. It supports people with visual disabilities while also improving usability in everyday situations.

The principle is simple: important information should not disappear because of the colours chosen to present it.

Use colour confidently. Use it creatively. But make sure the experience remains clear for all audience, regardless of ability, age, or background.