Re: What Protein is used to distinguish colour in the cones of the eye?

Tom,
  Color in the cones is distinguished by several different closely related 
proteins called opsins. An opsin protein is attached to a molecule of 
vitamin A to form a molecule of rhodopsin. Anyway, normal people have 3 
different opsin proteins which all respond best to a certain wavelength, or 
color, of light.  The three colors which these three opsins respond best to 
are red, green, and blue.  Each cone has only one type of opsin, so every 
cone is either a red, green, or blue cone.
  People who are color-deficient or "colorblind" are missing either one, 
two, or all three of their opsins, and so are missing one, two, or all 
three types of cones.
  This is pretty much a simplification.  You're probably wondering, "If we 
only have 3 colors of cones, how the heck can we detect over a million 
separate shades and hues?  And what about yellow?"  The answers to those 
are a bit more complicated and get back into brain processing, so I'm not 
going into them right now.  But if you want to know, just keep asking 
questions!

Tom

p.s. I got my info from "Biochemistry" by Lubert Stryer.