Re: Color Blindness Was: Web site readability

["Nagai, Paul" <pnagai -at- VISA -dot- COM>]

> >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.
>
Avoiding the ontological discussion of perception (what is blue? does
everyone really see blue the same way?), I think a more empirical
statement than "color is perceived differently" would be "certain colors
are difficult to differentiate." The red-green color-blind male (most
common affliction) has difficulty distinguishing between red and green
... they register, to him, similarly.

Still, I think you should only think about this if you're designing
color schemes that are not part of the standard web "tools" ... i.e.,
don't change link colors, design your icon, border, menu colors to be at
least red-green friendly.

------
Paul Nagai


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