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Subject:Color Blindness Was: Web site readability From:Steve Fouts <stefou -at- ESKIMO -dot- COM> Date:Thu, 20 Aug 1998 09:41:24 -0700
Roy Anderson <royanderson -at- IBM -dot- NET> said:
>During my first large online help development project, I was
>surprised to discover approximately 20% of the entire male population
>is color blind.
I am surprised as well. The statistics I have seen generally vary
between 8 and 10%, usually depending on the number of Asian males in
the sample, as Asian males apparently have a lower incidence of color
blindness.
>Color blind people can detect varying colors as varying shades
>of gray, but reds and greens often pose detection problems for them.
This also is untrue. True color blindness, in which colors are
perceived as shades of gray, is almost nonexistent in the human
population. People who have color vision deficiencies have
"cross-over" problems. In a person with normal color vision, the Red,
Green, and Blue cones are activated by various wavelengths of light.
In a color deficient individual, wavelengths that would activate a
blue cone in a "normal" person will (for example) either activate
the wrong cone or fail to activate the blue cone. This results in the
color being perceived differently. You see green, I see brown, you
see purple, I see blue.
The way that this applies to the discussion of color changes in links
is that the colors chosen by the Mosaic team for link colors (and
therefor by the Netscape team, since some of them had been on the
Mosaic team, and I.E., since initially it was Mosaic) went from high
luminance for unfollowed links to low luminance for followed links (I
may have that backwards) so that the difference is detectable to a
wide range of viewers, even those with slight color vision problems.
If Joe Schmoe web page designer changes the colors, chances are he has
no idea what low luminance means, or if his color changes are
detectable to people with color vision problems. Chances are, he
doesn't care, either. Arrogant web page designers are a dime a dozen.
My guideline is, don't do it.
