When I was growing up, I can recall getting extremely excited every single year during the later portion of June. The reason for that excitement laid in the fact that at that point, in Long Island, the temperatures were finally hot enough for my family to open our pool in the backyard. That moment when my father would rip the thick, black winter cover off the top of the water’s surface was always a highlight of the summer. However, when that event finally occurred each year it was always such a tease; the water in the pool would be filthy with leaves, dirt, and dead insects that compiled throughout the off-season. Sure enough my brother, sister, and I would have to wait a few days longer for my father to clean the water with chlorine and other chemicals before it was safe enough for us to start swimming. However, the same problem arose every single year- my father could not align the colors properly on the chlorine testing strip because he has a color vision deficiency.

As many may know, a chlorine testing kit is a simple devise that a person can use to measure total levels of chlorine, hardness, cyanuric acid, pH, alkalinity, and many other properties of water in a pool. All the individual has to do is dip a test strip into the pool and then observe where the colors on the test strip align to the colors on the accompanying chart (located on the box of the kit). They all look something like this:

However, my father would have great difficulty distinguishing between certain colors after removing the test strip from our pool in the backyard, so he would always ask for my assistance. Although I loved doing this job each and every year, I always questioned why my father could not see the differences between the colors. I always just assumed that when he told me that he was “color-blind” he meant that he saw everything in black and white, like in old-school movies.

Consequently, now that I am older and have learned about color vision, I realize that my assumption about my father was incorrect. My father, like 8% of the male population and 0.5% of the female population did in fact have a color vision deficiency, but he did not see in black and white. There are many different types of defects and when I assumed that my father was completely unable to see color, I was assuming he was a cone monochromat or a rod monochromat (neither of which was really the case). Cone monochromats only have one cone type and rod monochromats have no cone of any type, which results in people with these defects being “truly color-blind.” This is because it’s impossible for them to see different wavelengths of light without multiple kinds of photoreceptors and those wavelengths from light reflection is what allows people to see colors in the first place. As it turns out, my father is actually color-anomalous (completely different than the two defects previously discussed), which means that he has two types of cones that are so similar that discriminations cannot be made based on them. In his particular case, he has very similar L-cones and M-cones, which means that he has difficulty differentiating between middle wavelengths and long wavelengths in the electromagnetic spectrum. The middle wavelengths are perceived as the greens and yellows by a majority of people and have wavelengths mostly between 500nm and 600nm. On the other hand, long wavelengths are perceived as the oranges and reds by a majority of people and have wavelengths mostly between 600nm and 700nm. As a result, my father, who has very similar L-cones and M-cones, has trouble telling the difference between green, yellow, orange, and red at times.

In the end, our pool in the backyard was always managed properly and my siblings and I enjoyed swimming just about every day of the summer. Even though my father had difficulty telling the difference between certain colors on the chlorine test strip, I was always able to lend a helping hand and make sure our chlorine, pH, and bromine levels were not too high or too low. I now understand that my father is simply color-anomalous, with similar L-cones and M-cones; he doesn’t actually see in black and white like I always assumed he did when I was a little kid.

Source for picture: http://blog.intheswim.com/beginners-guide-to-pool-water-testing/