Re: Colorblindness references

Doing lots of reading...

The conclusion must be that we do not know enough about what are real disorders to write them off as a continuum. What we should do is inlist help from people who do know what they are talking about. I wrote of to Achromatopsia.org. If anyone knows more people to write to, please do.

However that said, I will give you the fruits of my labor.

Two types of photoreceptors in the eye: rods and cones. Rods, which provide vision in dim light, have no ability to distinguish between colors. Cones are responsible for color vision
Color vision deficiencies result from either a lack of one or more cone types, or cones that behave differently from average

To have rod monochromacy, or congenital achromatopsia is totally colorblind or almost totally colorblind, and they have poor visual acuity. This is very rare.  Without normal cone vision, their eyes are not able to adapt normally to higher levels of illumination. There are many variations in the severity of these symptoms. There are complete rod monochromats, incomplete rod monochromats, and blue cone monochromats. Complete rod monochromats have the most severely impaired vision of all achromats

They cannot distinguish any hues (e.g., blue, green, yellow and red. They also have poor visual acuity, aversion to bright light and nystagmus (an involuntary, rapid movement of the eyes).

Cerebral achromatopsia (unlike other  achromatopsia ) report that they see a monochromatic world, all in shades of gray. (not accompanied by severely impaired vision, extreme light sensitivity, or any abnormality in the photoreceptors of the retina)

Dichromacy is a less severe form of color defect than monochromacy It is much much more common. Dichromats can tell some hues apart. Dichromacy is divided into three types: protanopia, deuteranopia and tritanopia. 

Protanopia and deuteranopia are red-green defects. Persons with red-green defects have difficulty distinguishing between reds, greens and yellows but can discriminate between blues and yellows. Protanopes often can name red and green correctly because green looks lighter to them than red.

Hereditary tritanopia is a blue-yellow defect. Persons with blue-yellow defects cannot see the difference between blues and yellows but can distinguish between reds and greens. (Less common.) 

Anomalous Trichromacy—The ability of anomalous trichromats to distinguish between hues is better than dichromats but still not normal. Red-green anomalous trichromacy is subdivided into protanomaly and deuteranomaly. A third type of anomalous trichromacy is tritanomaly. In fact, those suffering from any of these conditions do experience color, but not in the sense that a color "normal" observer does.



Some sites claim (and seem reputable) that with color deficits, ability to discriminate colors on the basis of all three attributes - hue, lightness and saturation - is reduced. Designers can help to compensate for these deficits by making colors differ more dramatically in all three attributes


To conclude with an opinion ( It is not ready for a proposal but could be the basis for one) 

For Dichromacy:
Avoid colors that depend on being able to differentiate:
    a.. Red-green 
    b.. blues and yellows
    c.. reds, greens and yellows 

So using colors that mix a blue with a red and a green with a yellow would work

Or hand control over to the user (so this is more important in an image then as a text color scheme) or provide alternative renderings...

For achromatopsia: 
Maintain high contrast in all color schemes.(Especially were control is not handed over to the user.)
Hand control over to the user.

How does that sound?

Needs more work..
    
    -----Original Message-----
    From: Dick Brown <dickb@microsoft.com>
    To: 'w3c-wai-gl@w3.org' <w3c-wai-gl@w3.org>
    Date: Sunday, January 28, 2001 9:11 AM
    Subject: Colorblindness references
    
    
    I took an action item to send some pointers to resources on colorblindness.

    Some of the resources below do in fact indicate what kind of combinations can often cause problems, and I think it would be appropriate for us to include those in techniques. I do not think we should *recommend* color schemes, especially in a checkpoint.

    Dick Brown, Microsoft

    
    
    Can Color-Blind Users See Your Site?  http://msdn.microsoft.com/voices/hess10092000.asp
    Columnist Robert Hess continues his series on color use. This time, he examines how color choices can affect site accessibility. (October 9, 2000)

    A site to simulate rendering for people with color vision problems:

    http://www.vischeck.com/vischeckURL.php3

    http://www.lighthouse.org/color_contrast.htm.

    
    
    From the Microsoft Windows Guidelines for Accessible Software Design at

    http://www.microsoft.com/enable/dev/guidelines/software.htm:

    Avoid Problematic Color Combinations 

    Summary: Avoid using colors that commonly cause problems for people with color vision anomalies.        

    There are a number of things that can be done to allow even individuals with color vision anomalies to be able to take advantage of the color-coded information: 

    -- Avoid using common pairs of colors that are indistinguishable by people with color perception anomalies. For example, avoid mixing green and blue, or red and green, red and brown, or white and light green.

    -- Use colors that differ significantly in hues and intensity

    -- Avoid muted colors with low luminance values (intensity).

    
    
             -----Original Message-----

            From:   Donovan Hipke  

            Sent:   Tuesday, November 28, 2000 3:23 PM

            To:     Gayna Williams

            Cc:     MSN Home Page Request; Dick Brown

            Subject:        MSN Color Schemes

            Hi Gayna.

            Seeing as how the home page supports color schemes, I thought it would be a good idea to explore high contrast ones that would liven things up for color blind users.  Do you have any data on what color combos/hues work well for this?

            Thanks!

            Donovan Hipke
            MSN.com Dev Team

            Pager: 1854874@skytel.com