If possible it would be nice to ask what kind of "color blindness" he has.

Normally color blindness doesn't mean the person cannot see color, but rather that they cannot see certain ranges of colors (depending on which type they have).

As far as color contrast goes we already have enough between the two. In all the normal types of color blindness (protanopia [1% M], deuteranopia [1% M], and tritanopia [<1% M&F), even when you cannot see red the red link is still a different colour from the blue link.
The only case where that is not true is full achromatopsia [0.0033%], where the person cannot see any color at all and in high-lighting situations (within the range of normal sunlight) cannot see anything.

((i.e: It would be nice to know if he has achromatopsia or if the problem is not the color contrast itself but a deeper problem with the use of color))


That being said it might be time to have a discussion about how good design does not use color alone to convey meaning.
The old preference that replaced redlinks with text followed by a question mark is questionable and did have good reason to be removed (I remember something about it existing because the precursor to MediaWiki and some other wiki engines rendered links that way, but it segmented the parser cache slowing down wikis like Wikipedia and was non-intuitive since while you can tell the difference between a link and a nonexistent page link the only way to get to the nonexistent page is by clicking a single question mark plus you can't tell how much of the text before the question mark is part of the link).

However the idea of displaying extra markup beyond the `new` class in redlinks is a worthy idea. Not as an accessibility preference, but as something that is always on, as accessibility should not be a default off preference.
The ideal way to do this would probably be to add an icon to the end of every redlink (maybe with a "page does not exist" alt text, depending on what screen reader flow sounds like). If we can't find a good culturally abstract icon then we could use a circle enclosed question mark and on mouse over even describe what a redlink is and invite the person to start the article.

~Daniel Friesen (Dantman, Nadir-Seen-Fire) [http://danielfriesen.name/]
On 2014-09-09 4:55 AM, Amir E. Aharoni wrote:
Hi,

Disclaimer: Though I worked in an accessibility software company for three years, I know almost nothing about color blindness, so this question may be silly.

A participant in a recent workshop for new Wikipedia editors workshop in Israel complained that he cannot tell red links from blue links because he is color-blind.

Has this issue ever been noticed or addressed by anybody?

The only related thing I can think of is the option to show links to nonexistent pages with a question mark, which was disabled on Wikimedia sites a year or two ago. Is there anything else?

Thanks.