Helping the color blind see their missing colors

G K GRAY gord at
Fri Jun 14 19:32:29 EST 1996

In article <Pine.3.89.9606141113.A22122-0100000 at>, Ron Blue (rcb1 at LEX.LCCC.EDU) writes:
>> How *different* is NJM III?
>Good question.  At this time I can not say.  For example, what if NJM III is
>only saying he is colour blind.
>>  I too am colour blind but not in the most common 
>> red-green or blue-yellow.  I cannot see purple or green.  Purple appears as 
>> blue and green as brown.  Is this rather uncommon?  
>Well yes in that the frequency is lower.  My wife said everyone else is
>color blind since they have such horrible color arrangements.  Since she is
>very good at it, sometimes I feel like agreeing with her.
>> {snip}
>> > When the opportunity arose, I showed Nevin Miller the subjective color
>> > illusion.  By rotating a black and white disk in florescent lightand timing
>> > the speed carefully one can see colors.  For the first time in Nevin's life
>> > he reported seeing a color that he has never seen before.  It was to me
>> > a bright blue-purple.
>> > 
>> What did NJM III mean by never before seeing this colour?
>Fair question.   Unfortunately when I tell you I see blue you can say I see 
>blue also.  This does not mean that the blue I am seeing is the same blue
>you are seeing.  But we should at least agree that the subjective report
>was concordant for different observers.  This can be at least an 
>operational definition.
> > There are  many times that I cannot identify a colour, particularly
>> when they are darker shades.  A "novel" colour may appear to me as dark
>> blue/black/red/brown.  Meaning that you 
>> could tell me it was either of these and I would have
>> to believe you.  Lighter 
>> shades of these same colours do not appear to be a problem.  Often I 
>> would have to say I had never seen these colours before.  How else could I 
>> explain my inability to distinguish these colours?
>>  Unless I have some kind of 
>> very selective colour agnosia.  Wouldn't that be a kick?  What
>> about NJM III?  
>> If you showed him the same colour illusion again does he
>> remember it as purple-
>> blue?
>I do not know.  But I will check it out IF someone is interested in doing
>a PET scan.
>> Anyways I was just curious.
>> > Nevin has reported a willness to be a subject.  I suspect that by using
>> > positron emission tomography that his report of purple stimulation will
>> > be identical to controls.  Nevin lives in the Allentown, Pennsylvania
>> > area.  Are you interested in doing the research?
>> > Ron Blue  rcb1 at
>> > 
>> Steve Madison
>> Neuromuscular Research
>> Laurentian University

        The most precise and wholely objective way to answer Steve's
question is to measure the exact wavelengths to which the retinal
cones are responding. 
        But frequency detection is only a first step in the process
of colour *perception*. As the experiment Ron described shows,
there must be further steps in processing the raw data received
from the cones, which can trick the ensuing circuitry into
perceiving colours the existing cones cannot report, for in the
normal complement there are but 3 types of cone, each of which is
"tuned" to one specific frequency in the visible spectrum. Genetic
defects can alter these frequencies or completely eliminate one or
more of them. 

Gordon Gray  gord at 

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