> I interpreted Bob's question to be "physical" (outside of the brain) and > "inability to interpret" (inside the brain). Both are actually physical and most > color blindness as you say is inherited. Hey, it was only an aside ;o) Physical, in the sense used, would mean that the retina lacked a certain class of cones making it impossible to distinguish between certain tones. Reading a little this seems to be the main explanation "Ability to Interpret", whilst still arguably physical, could have no identifiable defect - oh heck, "Synaesthesia" comes into the same category ... it's in the brain things get muddled.
