Color contrast – Needs manual check

Color contrast – Needs manual check appears in the Accessibility Checker in Adobe Acrobat Pro for every document. Acrobat doesn't measure the contrast between text and its background. Instead, it asks you to check by hand that text stands out enough for people with low vision or color blindness to read it, as WCAG 2.1 requires.

What this means

WCAG 2.1 success criterion 1.4.3, Contrast (Minimum) (opens another website), sets two ratios:

• At least 4.5:1 between normal text and its background.
• At least 3:1 for large text, which WCAG defines as at least 18 point, or at least 14 point if it's bold.

Text in a logo or brand name, and purely decorative text, doesn't have to meet the ratio. Everything else does, including text inside images, such as a scanned flyer or the labels on a chart.

Two related WCAG checks also need a person, and they're easy to miss:

• 1.4.11 Non-text Contrast: the lines, bars and areas in a chart, and the borders of form fields, need at least 3:1 against the colors next to them.
• 1.4.1 Use of Color: color can't be the only way information is shown. "Overdue items are in red" fails unless there's also a label, symbol or pattern.

Adobe's help points to WCAG 1.4.3 for this rule. It also mentions Acrobat's Replace Document Colors preference (in Preferences > Accessibility), which lets an individual reader view a document in high-contrast colors. That helps the reader who turns it on, but it doesn't change the file, so it isn't a fix.

Why it matters

Low contrast affects people with low vision, people with color blindness and many older readers. It also affects anyone reading on a phone in sunlight or printing in grayscale. Light gray body text, white text on pale colored boxes and colored headings are the usual problems in agendas, newsletters and reports.

How to fix it in Acrobat Pro

Acrobat can't measure contrast for you, so this is a check-then-fix process:

Fix it in the source file

Colors are much easier to fix where they were chosen:

• Word and PowerPoint: run Review > Check Accessibility before exporting. Microsoft's checker gives a warning when text doesn't have sufficient contrast with its background, although in PowerPoint it skips some objects, such as transparent text boxes. Pick theme colors that pass, so every new document starts from good colors.
• InDesign: set up swatches with tested contrast once, and use only those.
• Charts: add data labels, patterns or direct labels so the chart works without color, and check the contrast of lines and bars against the background.
• Templates: fix contrast in your templates and every document made from them improves.

Fix it automatically with Includoc

Includoc measures the contrast of real text against its background and flags text that may fall below 4.5:1, or 3:1 for large text. This is an estimate based on the drawn colors, so treat flagged items as "look at this", not as a final verdict.

We don't redesign documents, so we don't change colors for you. Fix them in the source file and export again. Text inside images and charts can't be measured reliably, so it appears on our "needs human review" checklist, along with checking that color isn't the only way information is shown.

Standards

Related errors

• Logical Reading Order – Needs manual check: Acrobat's other check that always needs a person.
• Accessibility: Investigate: Microsoft's checker, which does flag low-contrast text in Word, PowerPoint and Excel.

To see which requirements come from WCAG and which from PDF/UA, read WCAG vs PDF/UA, or check a PDF free to find text that may have low contrast.