Short answer
Anything a person can perceive without telling hues apart: text, an icon or symbol, an underline, a pattern or texture, a change of shape, position or weight, or — in some cases — a clear difference in lightness. WCAG 2.2 criterion 1.4.1 requires that colour is never the only visual means of conveying information, so the practical test is to remove the colour and see whether the meaning survives.
The criterion exists for sighted people who cannot rely on hue: people with colour-vision deficiency, people with low vision whose colour perception is reduced, older users, and anyone using a monochrome display, a greyscale print, or a screen in bright sunlight. Its wording covers four things: conveying information, indicating an action, prompting a response and distinguishing a visual element. The W3C's examples are deliberately mundane — required form fields marked in red, and a diagram whose elements are identified by colour, fixed by adding numbers. It is a Level A criterion, the most basic level of conformance, and unlike the contrast criteria it has no ratio: it is a yes-or-no question about whether another cue exists.
Inline links distinguished from body text only by colour are the textbook case. The W3C's sufficient technique G183 allows a colour-only link if its lightness differs from the surrounding text by at least 3:1, on the reasoning that a 3:1 luminance difference is itself a non-hue cue. The table shows how hard that is to meet. Against black body text, the classic dark link blues (#0000EE, #0645AD) fall well below 3:1; only lighter blues such as #1A73E8 pass, and that one only just reaches 4.5:1 against the white page. Against a softer #333333 body text, none of the five colours tested passes. The W3C itself notes that dark colours can be hard to tell apart even at 3:1. In practice, underlining links in running text is the simplest reliable answer; links in navigation bars and button-like links are already distinguished by position and styling.
Visited-link colour is a special case: browsers restrict how :visited can be styled, so the W3C does not treat a colour-only visited state as a 1.4.1 failure.
Strong second cues carry the meaning on their own: a text label ('Error: enter a date'), an icon with a distinct shape (a tick versus a cross, not two identical circles in different colours), an asterisk with a legend for required fields, an underline, a bold weight change, a pattern fill, or a position (negative bars below the axis). Weak second cues are technically non-colour but easy to miss: a one-pixel border change, a slightly different shade of grey, or an icon that only differs in colour. A good check is whether the second cue would work for someone reading a greyscale printout at arm's length. If it would, it is doing its job; if it relies on seeing a small detail, it probably is not.
Beyond links, the recurring failures are predictable. Form fields that turn red on error with no message. Status dots (online, away, busy) that differ only in hue. Calendar days where availability is shown by green and red cells. Charts whose legend is a row of coloured squares with no direct labels. Required fields shown by a red label colour. Selected tabs shown only by a colour change. In each, the fix is to add the second channel, not to change the colours: better colours help people with mild colour-vision deficiency but do nothing for someone reading in greyscale. The criterion does not forbid colour — it asks that colour reinforce, not carry, the meaning.
| Link colour | Against white page | Against #000000 body text | Against #333333 body text |
|---|---|---|---|
| #0000EE | 9.39:1 | 2.23:1 — needs underline | 1.34:1 — needs underline |
| #0645AD | 8.52:1 | 2.46:1 — needs underline | 1.48:1 — needs underline |
| #1A73E8 | 4.50:1 | 4.66:1 | 2.80:1 — needs underline |
| #0B57D0 | 6.38:1 | 3.28:1 | 1.97:1 — needs underline |
| #2E7D32 | 5.12:1 | 4.09:1 | 2.46:1 — needs underline |
Why: Links differ from body text only in hue, at under 3:1 lightness difference.
Fix: Underline inline links.
Why: The requirement is conveyed by colour alone.
Fix: Add 'required' text or an asterisk explained at the top of the form.
Why: The dots differ only in colour.
Fix: Use distinct shapes or add a text label or tooltip.
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
StandardStrong evidence
WCAG 2.2 success criterion 1.4.1 (Level A) requires that colour is not used as the only visual means of conveying information, indicating an action, prompting a response or distinguishing a visual element.
Source: Web Content Accessibility Guidelines (WCAG) 2.2; Understanding Success Criterion 1.4.1: Use of Color (WCAG 2.2)
StandardStrong evidence
W3C technique G183 treats a contrast of at least 3:1 between inline link text and surrounding text as a way to meet 1.4.1 where links are distinguished by colour and lightness, while noting that dark colours can remain hard to tell apart at that ratio.
StandardStrong evidence
The W3C's Understanding document explains that colour-only visited-link styling is not treated as a failure of 1.4.1 because browsers restrict how the :visited state can be styled.
Source: Understanding Success Criterion 1.4.1: Use of Color (WCAG 2.2)
Colourwise analysisStrong evidence
The classic link blues #0000EE and #0645AD have less than 3:1 contrast with black body text, and none of five common link colours tested reaches 3:1 against #333333 body text, so such links cannot rely on technique G183 and need an underline or other non-colour cue.
Based on: Computed by Colourwise with the WCAG 2.2 contrast formula; see the table.
Source: Technique G183: Using a contrast ratio of at least 3:1 to distinguish inline text links from surrounding text; Web Content Accessibility Guidelines (WCAG) 2.2
Reviewed 29 September 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.