Color Blindness

I mentioned in my last post that I can't titrate very well due to my inability to differentiate various shades of pink well. This, of course, stems from my red-green color blindness.

As many of my readers are aware, I have a number of perceptual issues with regards to color as a consequence of being red-green color blind. One of which is that I perceive certain extremely pale shades of (what people tell me is) pink as gray. I discovered this after I purchased a sweatshirt in our nation's capitol that appeared quite gray to me. Later, faced with overwhelming and independent opinion that it was pink, I was forced to concede that it must indeed be pink.

As it turns out, I'm not too good at differentiating certain shades of pink and purple either. And the odd shade of blue will appear purple to me (but that's rare). But the best way to sum up the most common effect of my color blindness is that I have a hard time seeing small red or orange flowers in fields of greenery.

Of course there are some other practical problems. I often have difficulty making out color on the thin lines of things like card and tile games (especially the unfilled single shapes on Set cards). This predisposition in concert with bad lighting or a poor angle will make the colored lines on the card appear black to me. If I do get a hint of color, my mind will fill in the color; and the card will then appear that color--but not always the correct one. Some of my readers have found it amusing to continually find new ways to elict this response.

Make no mistake about it though, I can see the red and the green of the stoplight just fine.

The wonder of red-green color blindness is that it's a sex-linked trait. It's a recessive trait whose gene only appears on the X chromosome. As a result, men only need one such gene to exhibit color blindness; while women need both chromosomes to carry the recessive gene in order to be color blind. Depending on whose statistics you believe, ten to fifteen percent of the white male population experiences it to some degree. Meanwhile, it affects less than half of one percent of the female population.

My brother and I are both red-green color blind. Although it doesn't matter, my father isn't color blind (he could only pass on the trait to a daughter). We must have inherited this lovely trait from my mother. We're not enitely sure if she became a carrier by way of her mother, or if my grandfather wasn't perhaps red-green color blind and didn't know it.

I had no idea that I was red-green color blind until my younger brother was tested for it early in elementary school. A year or two later I was tested; and much to my surprise, I couldn't see some of those fabled numbers in the dot patterns. Heck, for all I know there aren't any numbers there.

For your edification, I present to you a handful of Ishihara color blindness dot tests. You should be able to quickly see distinct numbers amidst the dot patterns. Due to the variance of color calibration and the transmitted light enviornment monitors provide (as opposed to a reflected one), these tests may be less accurate than their printed counterparts. Just the same, they generally work on me. I can only see the first two and part of the third. The rest are just dots to me. I'll publish the numbers behind the dots in a comment, so you don't cheat subconsciously.


Test 1


Test 2


Test 3


Test 4


Test 5


Test 6