http://en.wikipedia.org/wiki/Cerebral_achromatopsia
The Case of the Colorblind Painter
The most famous instance of cerebral achromatopsia is that of "Jonathan I." immortalized in a case study by Oliver Sacks and Robert
Wasserman, and published as The Case of the Colorblind Painter. The essay tracks Johnathan I.'s experience with cerebral
achromatopsia from the point where an injury to his occipital lobe leaves him without the ability to perceive color, through his
subsequent struggles to adapt to a black, white and gray world, and finally to his acceptance and even gratitude for his condition.
Especially pertinent is the analysis of how cerebral achromatopsia affects his practice as a painter and artist. Descriptions of
cerebral achromatopsia's effects on his psychological health and visual...

On May 30, 8:49 pm, Sir Frederick fuzzysys.com> wrote:

The explaination at the link you provided leads me to believe that
some of the various areas of visual filtering can be trained to do
other things than they evolved for since the visual cortex is a rather
complex adaption of moduals each with different abilities to interpret
differently the same inputs.

The critical difference between cerebral achromatopsics and people
with other forms of color blindness is that cerebral achromatopsics
retain the ability to perceive chromatic borders. For example, they
see a red square on a green background effortlessly even when the red
and green are equally bright. There are various ways of ruling out a
role for unintended luminance differences in accounting for this, e.g.
random luminance masking. It even appears that cerebral achromatopsics
can discriminate contrasts on the basis of color direction, but they
can't use these contrasts to compare the color of surfaces that do not
adjoin directly. It has been suggested that cerebral achromatopsia
might best be seen as a failure in specific color-constancy
mechanisms.