Perceiving Color in Nature

Part of the wonderful experience of being outdoors involves taking-in the beautiful scenery. Imagine it - going out for a trail hike during that sweet-spot moment when Fall leaves are at their peak. I've heard many people talk about how amazing Fall colors can be. Unfortunately, I don't think I fully appreciate the sentiment because I am red-green color-blind. A protanope to be exact but that really isn't specific enough. Even among those, mostly men, who are color deficient, there is individual variability. For me, I have the inherited condition given to me by my mother. It involves having a mutant set of color receptor cones in the eyes that process red and green differently than normal. But there is an interesting story for how this was discovered and what it means for people with the heritable trait!

First, I want to show you what it's like to see through my eyes. It's probably not what you'd expect. It is, however, the question that rakes most people's mind when they find out I'm color blind. I know this because the first questions I am asked when I tell people I'm color-blind is, [points to object] "what color is this?" I'm usually inclined to play along because they're interested and, let's be honest, it's not the worst question to ask. The hard part for me is not being able to convey what objects look like through my eyes. Worse still, I have no clue what the same objects look like to most other people. But for now I can at least satisfy the former by offering you a side-by-side comparison of two images: one is the original image while the other is filtered to distort the original colors in such a way as they appear to me. See if you notice the difference.

Truth be told, the filter isn't perfect. I can see a bit of difference between the first two side-by-side images. It appears that there is a bit more green in the left image. The bottom images look identical to me. Not even sure if I did it right. But there you have it. To many protanopes, these side-by-side images are indistinguishable. Now for the fun part: science.

The human eye usually has 3 color receptor cones that feed ganglion cells information about light wavelength that is interpreted as color in the brain. (Food for thought: color doesn't exist outside your brain.) People with a normally functioning set of three cones are called trichromats. These cones are broken down as follows:

• White/Black - responsible for tints and shades
• Yellow/Blue - responsible for distinguishing yellow and blue
• Red/Green - yep, you guessed it... 

In 1948, Dutch scientist H.L. de Vries was studying functional differences in color-blind men who possessed a mutant cone that is less sensitive to either green or red, making it difficult for them to distinguish the two colors. To test their ability to match colors, de Vries had the men look at a standard color swatch of yellow and, in a separate swatch, mix colors by turning knobs so that the result, to their eyes, matched the standard yellow swatch. What he found was that, to compensate for their difficulty in discerning hues, they needed to add more green or red than normal-seeing people to make the colors match.

What's more interesting is that, while trying to determine if this color-blind trait was heritable, de Vries tested the daughters of one individual and discovered that, even though they were not color-blind, they needed more red in their test light than normal people to precisely match the color swatches. What de Vries stumbled upon wouldn't be re-evaluated for another 30 years or so and not extensively investigated until the late '90s (Reagan & Mollon, 1997; Jordan et al., 2010). In the mean time, de Vries surmised that red-green color-blindness ran in families, affecting men but not women. He also concluded that, while men had two normal cones and one mutant cone, mothers and daughters of color-blind men had the mutant cone AND the three normal cones - a total of four separate cones in their eyes. This early work described a new set of individuals who possess 4 color receptors. They are known as anomalous trichromats or, more popularly, as tetrachromats. They are usually (if not exclusively) women and they have the ability to detect wavelengths of light not perceived by normal trichromats. 

So, if you are either the mother or daughter of a guy who is red-green color blind, you might be seeing the world a bit differently than most of your peers. For those guys out there with the mutant cone (myself included), fear not - there could be something on it's way that will help us distinguish those pesky colors that usually give us trouble. A friend of mine (thanks Kelly!) just sent along an article by BuzzFeed about a business venture between ValSpar paint and the company EnChroma to develop tinted glasses to help the color-blind. The original BuzzFeed article can be found here. I'm familiar with the idea because it uses the same filtering principles used to distort the images I posted above. In doing so, it alters the wavelengths of light that are otherwise indistinguishable by the color-blind into visible colors. Google chrome introduced a lab plugin for their web browser - Chrome - that works the same way (i.e. Daltonize). I have been using it for about a year and it's pretty neat. I'll show you a demonstration below using the pics posted above.

Unfiltered                                      Filtered

To be honest, I don't know how helpful those tinted glasses will actually be but I'm interested in getting a pair. Maybe once the price dips a little. At $350-$400, they're a little pricey!