How to test contrast in digital documents?

Ensuring adequate color contrast in PDF documents is one of the simplest, yet most frequently overlooked principles of digital accessibility. Text that is too light, a pastel background, or thin letters can make even a well-prepared document difficult to read. The Color Contrast Analyzer allows for a quick assessment of whether the colors used meet WCAG requirements and if the content is sufficiently legible for all users. This tool supports the process of creating digitally accessible documents, although it does not replace more detailed checks, which should also include the structure and semantics of PDF files.

E-documents and digital accessibility – why is contrast so important?

Appropriate contrast between text and background is one of the foundations of digital document accessibility. Too low a difference in color brightness makes the content difficult to read, especially for people with low vision, seniors, or those using lower-quality screens.

WCAG standards require a specific level of contrast, as it directly impacts text legibility and the comfort of information reception. Therefore, when creating PDF files, it is worth including simple tests that quickly assess whether colors have been chosen correctly. The Color Contrast Analyzer is such a tool.

What is the Color Contrast Analyzer (CCA) tool?

Color Contrast Analyzer (CCA) is a free tool that allows you to check whether the contrast between two colors (text and background) meets WCAG requirements.

The tool is often used in digital accessibility audits because it allows for a quick assessment of whether a PDF document or website is legible for users with diverse needs.

CCA is available for Windows and macOS. Once launched, the user has access to a color picker (pipette) and a panel that displays the test result, along with information on whether the color pair meets WCAG AA or AAA standards.

How does CCA work and when should you use it?

The tool is simple to use. After launching, you use the color picker to select the text color, and then the background color. The application automatically calculates the color contrast ratio and indicates whether the given combination is acceptable.

CCA is particularly useful when preparing:

• PDF documents with a large number of headings, tables, or charts,

• leaflets and promotional materials in graphic file formats,

• forms and text documents with colored backgrounds,
• presentations that must remain legible after conversion to PDF.

Testing contrast in PDF documents – step by step

The process of using the Color Contrast Analyzer (CCA) tool is intuitive. After downloading and installing the software on Windows or Mac, you need to open the document to be tested and the tool itself, which consists of sections for foreground color (text), background, and results.

Colors can be entered in two ways: by directly typing HEX codes (color names, e.g., #00FF00), which can be extracted from text formatting settings, or by using the Color Picker (pipette) to click directly on the selected element on the screen.

CCA will immediately calculate the contrast ratio and, in the results section, indicate whether the combination meets WCAG AA criteria (required by Section 508 standards) or AAA for different text sizes and graphic elements. The tool may display, for example, 4.5:1. This result indicates the brightness ratio between the colors.

If the test result is negative, the tool offers a unique function to improve contrast using brightness sliders – once a satisfactory result is achieved, simply copy the new HEX code and update it in the source document. To ensure full accessibility, this process should be repeated for all color pairs present in the file.

 

Screen.1 Using the CCA tool (sourcesource: https://www.section508.gov/training/create/making-color-usage-accessible/color-contrast-analyzer/ )

 

Examples of correct and incorrect contrasts

Often, what we perceive as a modern and minimalist color scheme turns out to be the biggest enemy of digital accessibility. In editorial practice, the line between aesthetic minimalism and illegibility is very thin. Using the Color Contrast Analyzer allows for a rigorous verification of design assumptions – this tool objectively exposes the weak points of documents.

Example 1: Critical lack of legibility

In the example below, we see an attempt to combine bright red text (#FF1900) on a blue background (#3449FE).

• Test result: The contrast ratio is only 1.5:1.

• Analysis: This result is definitely below any standards. The CCA tool displays red “Fail” icons for all categories: standard text, large text, and interface elements.

• Why this is an error: Such a low combination causes the phenomenon of color vibration, which is tiring for any reader, and for people with visual impairments (e.g., color blindness), it makes the text almost completely blend with the background. A document with such parameters is considered digitally inaccessible.

 

Screen 2. Example of an error in CCA (source: https://www.section508.gov/training/web-software/andi-training-videos/color-contrast-analyzer/)

 

Example 2: Full digital accessibility

The second example presents a model situation – the classic combination of black text (#000000) on a white background (#FFFFFF).

• Test result: The contrast ratio is a maximum of 21:1.

• Analysis: The CCA tool displays green “Pass” icons in all fields. This combination meets the most stringent requirements of the AAA.

• Conclusions: This is the safest choice for long passages of text in PDF documents. It guarantees that the content will be legible even in difficult conditions (e.g., strong sunlight on a laptop screen or older smartphone models).

Screen 3. Example of a correct result in CCA (source: https://www.section508.gov/training/web-software/andi-training-videos/color-contrast-analyzer/)

 

If, during document testing, CCA indicates a “borderline” result (e.g., 4.4:1), it is worth using the program’s built-in sliders to slightly darken the text color and achieve the required 4.5:1.

Color contrast and WCAG requirements

The WCAG guidelines include three key contrast assessment levels:

• minimum contrast (WCAG 1.4.3): at least 4.5:1 for standard text,

• contrast for large text: at least 3:1,

• AAA level (WCAG 1.4.6): 7:1 contrast for highest legibility.

It is worth remembering that contrast applies not only to text but also to icons, buttons, and other non-text elements, which must maintain adequate visibility.

CCA limitations – what the tool won’t tell you?

CCA only examines contrast. It does not analyze document structure, assess the correctness of tags in PDFs, or check reading order.

The tool cannot assess whether the background was created from multiple graphic layers or if the text is on an image with variable brightness. In such situations, the result may be ambiguous and require additional verification.

Therefore, contrast testing is only part of the process of ensuring digital document accessibility. A file may meet contrast requirements but still be illegible for users of screen readers.

SAT PDC support – comprehensive content analysis

The Color Contrast Analyzer checks only one element of accessibility. In practice, for a document to be truly accessible, it should meet many other criteria.

The SAT PDC platform was designed to analyze a broader range of accessibility. It analyzes entire PDF documents, not just their color scheme. It identifies missing headings, incorrect tags, incorrect reading order, or missing alternative texts. This allows document creators to correct all key elements, not just contrast.

Wojciech Polar, a digital accessibility expert, points out that contrast testing is only the first step towards improving digital document accessibility:

– The most important thing is that solutions supporting the document creation process, such as SAT PDC, ensure full compliance with WCAG guidelines. A document must be perceivable, operable, understandable, and robust. Contrast analysis alone is not enough if the file does not have a correct tag structure, and headings, lists, tables, or forms are not marked correctly. Only a combination of actions – contrast tests, PDF structure assessment, and semantics correction – provides real digital accessibility.

Contrast in digital documents – summary

The Color Contrast Analyzer is a simple but very helpful tool for assessing document legibility. It allows for a quick check of whether text is sufficiently clear and meets WCAG 2.1 requirements. Although it is important support, it does not replace a full digital accessibility analysis of documents.

For a PDF document to be truly accessible, it must have a correct structure, proper reading order, alternative descriptions, and clearly defined headings. Public institutions should primarily ensure a comprehensive assessment of these elements, as according to the Act of April 4, 2019, on the Digital Accessibility of Websites and Mobile Applications of Public Entities they are obliged to publish digitally accessible documents.

 

Sources:

https://www.section508.gov/training/create/making-color-usage-accessible/color-contrast-analyzer/

https://vispero.com/color-contrast-checker/

https://www.section508.gov/create/making-color-usage-accessible/