Fill in a form wrong and watch what happens. A field turns red. Maybe a thin red border, maybe red text. To you that reads instantly as "fix this." Now imagine you cannot tell red from the grey and green around it - the border just looks like a border, the text just looks like text, and nothing tells you which field to go back to. You are not confused because you are careless. You are confused because the site put the entire message into a colour you cannot see, and left no other clue. This is one of the oldest and most common accessibility mistakes on the web, it has a WCAG rule of its own, and that rule sits at the most basic conformance tier - the one Ontario actually enforces.
Key facts
- WCAG (Web Content Accessibility Guidelines) Success Criterion 1.4.1 Use of Color is Level A - the most basic conformance tier - and has been in the standard since WCAG 2.0 (W3C).
- The rule: colour must not be the only visual means of conveying information, indicating an action, prompting a response, or distinguishing one element from another (W3C).
- Colour vision deficiency is commonly cited as affecting roughly 1 in 12 men (about 8%) and 1 in 200 women, with an estimated 300 million people worldwide (Colour Blind Awareness).
- Ontario's IASR (Integrated Accessibility Standards Regulation, O. Reg. 191/11) s.14 requires organizations with 50 or more employees and the public sector to meet WCAG 2.0 Level AA on public websites - and Level AA includes every Level A criterion, so 1.4.1 is inside that floor (ontario.ca).
- The next ACR (Accessibility Compliance Report) for organizations with 20 or more employees is due December 31, 2026 (ontario.ca).
What does "Use of Color" actually require?
Less than the name suggests, and nothing you have to give up. The rule does not ban colour, and it does not say "stop using red for errors." Colour is a fast, effective signal for the people who can see it, and you should keep using it. What 1.4.1 says is narrow: colour cannot be the only signal. Whenever you are using colour to tell the user something - this field is wrong, this word is a link, this order shipped, this seat is taken - there has to be a second cue that does not depend on seeing the colour.
That second cue is usually small. A red error field also gets an error icon and a line of text naming the problem. A link inside a paragraph gets an underline, not just a different colour. An "in stock" row gets the word "in stock," not only a green dot. A required field gets the word "required" or an asterisk with a legend, not only a red label. In almost every case the fix is to add a shape, a word, or a pattern alongside the colour you already use. You are not removing anything. You are making sure the message survives when the colour does not land.
Where does colour-only information hide on real sites?
In the places you would least expect, because whoever built the page could see the colour and never noticed the gap. A few patterns show up again and again.
The classic is the link that is only a different colour from the text around it - no underline, no bold, nothing but a hue. Turn the page greyscale in your head and those links vanish into the paragraph. The second is form validation: fields and messages that go red on error and green on success, with the colour carrying the whole meaning. That is exactly where this rule overlaps with getting the form itself accessible, and it is the one that quietly costs you completed checkouts. Then there are status indicators everywhere else - a green or red dot for availability, a coloured tag for "sale" or "sold out," a chart where the only way to tell two lines apart is that one is blue and one is orange, a calendar where booked and free days differ only by shade. Each of these is a place where a colour-blind visitor, or someone on a cheap screen in bright sun, gets less information than everyone else.
None of it means the colour has to go. It means the colour needs a companion.
Isn't this just the contrast rule?
No, and the difference is worth getting straight, because sites often pass one and fail the other. The contrast rule (1.4.3) is about legibility - is there enough light-dark difference between text and its background that a person with low vision can read it at all. Use of Color (1.4.1) is about meaning - are you relying on which colour something is to communicate. Your link can have perfect 21:1 contrast against the page and still fail 1.4.1 because, with strong contrast or not, the only thing marking it as a link is that it is blue. They are separate checks, at separate tiers - 1.4.1 is Level A, 1.4.3 is Level AA - and a site can trip either one on its own.
How do you check it, and what's the risk in Ontario?
You can sanity-check most of your site in a few minutes, and the trick is to take the colour away:
- Look for colour doing a job on its own. Walk your key pages - checkout, forms, product listings, dashboards, any chart - and ask of every coloured cue: if I could not see this colour, would I still get the message? Error states and in-body links are the usual offenders.
- Desaturate the page. Browser dev tools, an extension, or your operating system's greyscale mode will strip the colour out. Anything that becomes ambiguous in grey is a 1.4.1 problem - a link you can no longer find, a red field that now looks identical to a valid one.
- Add the second cue. An underline for links, an icon and a text message for errors, a label or pattern for status. Small changes, and they help everyone, not only colour-blind users - the extra clarity reads better on a phone in daylight too.
A note on tooling: an automated scanner catches some of this - it can flag a link distinguished only by colour - but it cannot judge intent, so it misses most status and chart cases. This is another reason a scan is not an audit: deciding whether colour is "the only cue" takes a human eye, not a crawler. A bolt-on widget does not help either, since an overlay cannot rewrite the meaning your markup fails to carry.
On stakes, the honest picture is the same one that applies to every barrier. In Ontario the AODA (Accessibility for Ontarians with Disabilities Act) has no private right of action, so no one sues you under it directly; the live route for an individual is a complaint to the HRTO (Human Rights Tribunal of Ontario) under the Ontario Human Rights Code, and that is how a single complaint actually unfolds. If you sell into the United States, a form no one can correct or a link no one can find is the kind of barrier that shows up in ADA (Americans with Disabilities Act) web claims. The durable answer is not a disclaimer - it is documented remediation: a dated record of what you found and fixed, which is what an honest ACR should reflect by December 31, 2026.
The reassuring part: because 1.4.1 lives at Level A, the fixes are usually the cheapest kind - a word here, an underline there, an icon on an error. Basic tier, basic effort, and it closes a gap that shuts real customers out of the exact pages you most want them to finish.
See whether your forms, links, and status cues lean on colour alone, and check for other accessibility issues - free Vayle Report, about 30 seconds: vayle.art. It detects overlay widgets, surfaces real WCAG failures, and tells you exactly what legally applies to your organization in Ontario. No obligation.
Vayle is a remote-first accessibility-engineering studio serving Ontario. General information, not legal advice.