The objective of this failure is to avoid situations in which people who cannot perceive
color differences cannot identify links (when people with color vision can identify
links). Link underlines or some other non-color visual distinction are required (when
the links are discernible to those with color vision).
While some links may be visually evident from page design and context, such as navigational
links, links within text are often visually understood only from their own display
attributes. Removing the underline and leaving only the color difference for such
links would be a failure because there would be no other visual indication (besides
color) that it is a link.
Red and Pink are the same color (hue) but they have different lightness (which is
not color ). So red and pink would pass the requirement for "not distinguished by
color (hue) alone" since they differ by lightness (which is not color) - as long as
the difference in lightness (contrast) is 3:1 or greater. For example, if surrounding
text is RED and the link is PINK it would pass. Similarly a light green and a dark
red differ BOTH by color AND by lightness so they would pass if the contrast (lightness)
difference is 3:1 or greater before focus or pointing.
There is no requirement that links be identifiable by people who cannot perceive color
if they are not perceivable for those with color vision. (e.g. if the links are hidden
for everyone – as in a game or test).
If the non-color cue only happens when the mouse hovers over the link or when the
link receives focus, it is still a failure.
If the link is a different color and bold it would not fail because the boldness is
not color dependent.
Examples
Example 1: Links with no underlines and similar contrast to body text
A Web page includes a large number of links within the body text. The links are styled
so that they do not have underlines and are very similar in color to the body text.
This would be a failure because users would be unable to differentiate the links from
the body text.
Example 2: Removing the underline from a link in a sentence or paragraph without providing
another visual cue besides color
<head>
<style>
p a:link {text-decoration: none}
p a:visited {text-decoration: none}
p a:active {text-decoration: none}
p a:hover {text-decoration: underline; color: red;}
</style>
</head>
<body>
<p>There are many resources to find out more about the
<a href="rain-in-spain.html">rain in spain</a>.
</p>
</body>
If the visual cue is only provided on hover (as in the example above), it would still
fail.
Check that each link in the page that is identifiable by color (hue) is visually identifiable
via some other means (e.g., underlined, bolded, italicized, sufficient difference
in lightness, etc).
Expected Results
If check #1 is false, then this failure condition applies and the content fails this
Success Criterion.