Neil 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. Roy 8888888888888888888888888888888888888888888888888888888888888888888 Bob, colour blindness has a purely physical basis. This is shown by its inheritance patterns. Neil That got me thinking: does colour blindness have a purely physical > basis, or is it in the inability to interpret?
