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Re: 1.4.1 use of color for state indicator

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From: Jonathan Avila
Date: Mar 9, 2020 6:54AM

> All the research into colour perception involves both hue and luminance, and the WAI colour contrast algorithm is based on both.

Yes, the contrast ratio does take into account more than lightness -- to help users with color perception challenges. That's why a contrast of >= 3:1 should be sufficient as it takes into account these other aspects.

Jonathan

-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Steve Green
Sent: Monday, March 9, 2020 8:50 AM
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] 1.4.1 use of color for state indicator

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Luminance isn't colour either. Every definition of colour I can find states that colour is the combination of hue and luminance. All the research into colour perception involves both hue and luminance, and the WAI colour contrast algorithm is based on both.

If the SC does not say what its authors meant it to say, then it needs to be rewritten. In the meantime, I do not see any justification for ignoring luminance. FWIW, I would argue against any change in the SC that equates hue to colour.

Steve


-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Jonathan Avila
Sent: 09 March 2020 12:42
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] 1.4.1 use of color for state indicator

If luminance was color then every single piece of content on a web page would be using color to communicate. Black text on a white background would be using color to communicate that it's text! A black border would be using color to communicate it's a border on a white background. The goal of the SC is to be able to differentiate -- if the author can differentiate sufficiently you can pass the criterion.

From the understanding docs -- "The intent of this Success Criterion is to ensure that all users can access information that is conveyed by color differences".

Jonathan

-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Steve Green
Sent: Monday, March 9, 2020 8:27 AM
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] 1.4.1 use of color for state indicator

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I don't agree with this view. Colour has two properties - hue and luminance, but neither is mentioned in either the normative text or the Understanding page. Only colour is mentioned.

F73 incorrectly states that hue is the same as colour and that luminance is not colour. This appears to be the only reference to hue, and it is factually wrong as well as being non-normative.

Steve Green
Managing Director
Test Partners Ltd


-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of Jonathan Avila
Sent: 09 March 2020 11:58
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] 1.4.1 use of color for state indicator

If something has contrast >= 3:1 then and that contrast communicates the meaning even when in grayscale then it would not fail the 1.4.1 Color requirement as Color (Hue) is not being used -- luminance is being used to communicate the difference.

So if you have a selected button that is inverted from the other colors and that selected state itself and the difference from the adjacent selected states >= 3:1 then it would pass. Comparison between non-adjacent selected states is something of a challenge as it's not clearly stated -- but I'd argue that if the difference between selected states only used luminance that was < 3:1 compared to the other selected state then it would not pass.

Jonathan

-----Original Message-----
From: WebAIM-Forum < <EMAIL REMOVED> > On Behalf Of glen walker
Sent: Monday, March 9, 2020 7:01 AM
To: WebAIM Discussion List < <EMAIL REMOVED> >
Subject: Re: [WebAIM] 1.4.1 use of color for state indicator

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Ok, maybe I need to ask for an opinion, then.

If you had to audit a site and the selected button had a black or blue background (unselected has a white background), would you pass 1.4.1? Or perhaps report it as a low priority failure and recommend they add another visual clue for the selected button but note that as it currently stands, most (if not all) users that can see the buttons will be able to tell which one is selected?

If so, then when would this issue move from a low to a medium or high priority issue? I have a real example where the default button has a white background (and black text) but the selected button in the group has a light orange background. The contrast ratio of of the white to orange is 1.8:1, but as mentioned originally, there isn't a requirement for contrast between states.

The buttons all have borders so the adjacent color contrast is ok (1.4.11).

Technically, the light orange background is "color only" just like the black background, but it sounds like the black background we would pass.

So what would you use to determine when a 1.4.1 pass becomes a failure?
Contrast?