I understand that we’ve got four different types of sensors on our retinas, the three cones that respond to red, green and blue and the rods.
I hypothesize that color blinded is caused by one or more of these being missing.
Am I close?
Yes. You are right on for the most common type of color-blindness, dichromatism.
The most common cause of color blindness is a genetic defect. The defective gene is carried on the X chromosome, so males are almost exclusively the victim, and white males make up practically the entire percentage of victims.
on the nose. if one of the three types of cones is missing, you have classic color blindness (red-green is most common, red-yellow (or maybe blue-yellow) much less so).
if you are missing two of the types of cones, you have monochromatic vision. although you are not truly seeing in greyscale, i don’t know that there is much of a difference.
jb
hey hey! tcburnett? long time, no read, man!
jb
Being colour blind myself, I doubt if I am missing one of the basic types of receptors. I am classic red-green colour-blind and I see all colours, including red and green. I just confuse a lot of shades.
It’s hard to explain… Browns and greens are tough. Some shades of purple look blue.
I’m guessing the receptors are present but defective. Or else the brain is wired wrong.
Or maybe we colour-blind folk are ok, and everybody else is wrong 
Colorblindness usually IS genetic… but it’s not as cut and dried as you’ve been told
First of all, there is a RARE type of colorblindness called achromatopsia, where the cones either aren’t there or don’t work. This results in monochrome vision. For more information, see The Achromotopsia Network Oliver Sach also wrote about this disorder in Isle of the Colorblind, and one of his short essays I can’t recall off the top of my head. This one is not sex-linked, by the way, but occurs 50/50 in men and women.
Moving right along… for more traditional colorblindness, you can either LACK one of the types of cones, in which case you can’t distinguish, say green from other colors (assuming it’s the green-sensing cones as fault) at all, or you can have “malfunctioning” cones which sense the particular color somewhat, but not like other folks.
Although MOST people who are colorblind are male, there are quite a few colorblind women, too, at least if you count the numbers (at 1% of the population that would still be 3 million in the United State alone). Women are less likely to be diagnosed as colorblind, though because, first of all, there is a strongly held myth that women CAN’T be colorblind, and secondly, because women MAY (it’s not conclusive) not alway be as badly affected by the defective gene for complicated reasons I don’t fully understand.
I learned a lot about this when it was discovered I was a deuteranomolus trichromat sorry, probably butchered the spelling on that which basically mean I really do have all three cones (the “trichromat” part) but the green ones don’t work quite as well as they should (the “deuteranolmous” part).
What does that mean? 99% of the time, jacksquat. I have no problem identifying trees and grass as green, or traffic lights, and so forth. There are shades that most people would call “green” that I might call “brown” or “blue” or “yellow”, but they’re the ones near the border already (don’t have problems with purple, unlike another poster). In fact, mine “problem” (which isn’t much of a problem) shows up if you test with something called “Ishihara plates” but pretty much nowhere else. It’s an extremely minor defect in my case.
Other colorblind folks might be more adversely affected.
Oh, and by the way - I am a colorblind woman. Yes, there are a few of us out there.
As I recall, the reason for colorblindness is (usually) not a lack of one of the types of color-sensing cone cells, but rather an inability to make the pigment necessary for the cone cells to work.
This is similar to your rods not working in bright light, since the pigments involved in the rod’s functioning is destroyed by bright light. So if you go from a bright area into a dark room, it takes time for the rod’s pigment to build up to the levels need for the rods to work.
All of the cone cells work by having specific pigments that allow them to respond to various wavelengths. If you don’t have the pigment for a certain wavelength (say red), then the cones that would normally detect red cannot work. You would then be “red color blind.”
It’s not that you LACK the pigment, usually, it’s that it’s defective. It doesn’t work as well, as opposed to not working at all.
While the degree of “color deficiency” remains constant in a particular person (in other words, I’ll make the same mistakes every time on a color vision test), it does vary from one person to another.
It’s a little distinction, but I DO get tired of people assuming I have no experience whatsoever of a particular color when in fact I do. It’s just not quite the same green you see.
Same thing that causes hairy palms.
Next question. 
I agree wholeheartedly. People assume that I can’t understand color at all, but that is nowhere near the case. I just can’t always accurately tell the name of the color, or properly differentiate among subtle shades.
My seven year-old son shakes his head sadly and says “Too bad Daddy doesn’t know his colors, yet.”
The stupidest thing someone has ever said to me: I had a job where I had to sort small slips of paper. The slips colored in faint pastel shades of blue, red, and white. They gave me a shadowy place to do the job. Still, I managed to sort the papers with about a 95 -98% accuracy. The small number of inaccurate sorts did no real harm to the process. Anyway, a frustrated supervisor, fussing about my shoddy sorting said “David, you’ll just have to TRY HARDER!!!” As if being colorblind has anything at all to do with how hard I “try”. :rolleyes:
No one has discussed how the gene is passed. As I understand it, it is passed through women, but shows in men. Therefore, my mother’s brothers are colorblind, but my mother is not. I am colorblind (because of my mother), but my children are not. My daughter’s sons will be colorblind.* My son’s daughters will be carriers (I think), therefore their sons (my great-grandsons) will be colorblind. *My daughter is actually adopted, so all bets are off on the genetics stuff. My son however, is my biological offspring.
In the case of a condition carried by a recessive gene on the X chromosome only:
Women have XX. Men have XY. The gene is only carried on the X. The gene is recessive, so if there are two X’s, and one does not carry the gene, then the person will not show the condition.
Your mother is a carrier. She has one X that carries the gene and one that does not. You got the one that does.
Assuming that your wife does not carry the gene, your sons cannot carry the gene. They would’ve inherited your Y chromosome which is free.
Your daughters will be carriers since they must’ve received your X that carries the recessive genes.
Assuming your daughters mate with men who do not carry the gene, of your daughter’s sons, 50% will inherit the recessive gene and show the condition, while 50% will be free.
If these assumptions do not hold, the odds change but can be calculated easily.
My mother-in-law is colorblind, and passed it on to my husband. I can’t remember if his type is red-green or blue-green, but he too has difficulty with shades. Without another color next to it to compare with, a red piece of paper could also be green or brown.
He has learned to identify colors by their frequency, or intensity. Because of his colorblindness, he is also more likely to spot things that are camoflaged (like in recon photos), as he focuses on patterns rather than colors!
In order to get a colorblind woman, assuming the standard sex-linked colorblindness, you need for the father to be colorblind, and the mother to be a carrier. If that’s the case, then half of all daughters will be colorblind. If both parents are colorblind, then all children will be. By contrast, to get a colorblind man, you only need for the mother to be colorblind. The upshot is that the rate among women is approximately the square of the rate among men, so if one in ten men is colorblind, then about 1 in 100 women will be.
To sum up all the possibilities:
Normal father, normal mother: All children normal
Normal father, carrier mother: Half of sons colorblind, half of daughters carriers. Other half normal
Normal father, colorblind mother: All sons colorblind, all daughters carriers
Colorblind father, normal mother: All sons normal, all daughters carriers
Colorblind father, carrier mother: Half of sons colorblind, half of daughters carriers, other half of daughters colorblind
Colorblind father, colorblind mother: All children colorblind
That’s why I chose my parents very carefully. _
Okay, let me get this straight. I am colorblind, but there was a 50 -50 chance that I wouldn’t be? My sister (same mother and father as me) has one son who is not colorblind. Will my sister’s grandchildren be affected at all by colorblindness (she has one son and one daughter)?