Color blindness: A mobile app demonstration

[sue_frantz]

Because the perception of color is inherent to our experience, it’s difficult to know what someone else’s perception of color is like. People with total color blindness (either monochromacy or achromatopsia) (National Eye Institute, 2015) or color deficiency – can’t know what someone with complete color vision sees. And people with complete color vision can’t know what someone with total color blindness or color deficiency sees.

In an article about what it is like to be a woman who is red/green color blind*, Zoe Dubno (2019) tells us about a free app that manipulates color to show us what everyone else is seeing: Color Blind Pal (Android/iOS/Mac).

If your students have one of these three types of color blindness, the app will shift the hue of colors to make those colors easier to see.

Protanopia/protanomaly (cannot see any red/reduced sensitivity to red)

Deuteranopia/deuteranomaly (cannot see any green/reduced sensitivity to green)

Tritanopia/trianomaly (cannot see blue/reduced sensitivity to blue)

For your non-color blind students who are, say, future software builders, website designers, graphic designers, interior designers or who will ever have a need to create a graph or do a presentation, they should know what almost 10% of their audience (National Eye Institute, 2015) will see. You can give your students this information from the National Eye Institute (2015):

Red/green color blindness

Protanopia: “Red appears as black. Certain shades of orange, yellow, and green all appear as yellow.”

Protanomaly: “Red, orange, and yellow appear greener and colors are not as bright.”

Deuteranopia: Red looks brownish-yellow; green look beige.

Deuteranomaly (most common): “Yellow and green appear redder and it is difficult to tell violet from blue.”

Blue/yellow color blindness

Tritanopia (very rare): “Blue appears green and yellow appears violet or light grey.”

Trianomaly: “Blue appears greener and it can be difficult to tell yellow and red from pink.”

Or your non-color blind students can see the effects of color blindness for themselves in the Color Blind Pal app. 

Or your color blind students who are, say, future software builders, website designers, graphic designers, interior designers or who will ever have a need to create a graph or do a presentation, can use the Color Blind Pal app to shift colors into a range they can better see. 

Instructions on how to use the Color Blind Pal app are at the end of this blog post.

Why is it that a red deficiency results in an inability to distinguish red from green and vice versa, and why is it that a green deficiency results in an inability to distinguish green from red?

Follow the link to this image that shows the light wavelengths and how many photons (packets of lightwaves) each cone captures. Notice how much the red and green cones overlap in terms of their sensitivity to the wavelengths of light. For someone who is lacking green sensitivity, for example, their spectrum shifts toward red, making telling the difference between red and green more difficult. Conversely, for someone who is lacking red sensitivity, their spectrum shifts toward green, also making telling the difference between red and green more difficult.

Why so much overlap between red and green cones?

It looks like red and green cones used to be different alleles of the same gene. And this is still true among New World primates. The continents split 50 million years ago separating what would become New World primates from Old World primates. Around 40 million years ago, in Old World primates what was the green/red gene duplicated, allowing one gene to specialize in creating red cones and the other to specialize in creating green cones. New World primates haven’t had this gene duplication and all remain dichromats (essentially, they’re red/green color blind), except for some females. Since the gene with red/green alleles resides on the X chromosome (and gene for blue cones on chromosome 7), a male New World primate has blue (chromosome 7) and either green or red (he only has one X). A female New World primate has blue (chromosome 7), and, with two Xs, she can have two greens, two reds, or a green and red. In the latter case, she is a trichromat (White, Smith, & Heideman, n.d.).

The Ishihara Test

After your students have had a chance to explore the Color Blind Pal mobile app, visit a website that displays examples from the Ishihara Test for color blindness, such as this one at colormax.org. Zoom in so that only one test item is displayed at a time. Your students who are not color blind can simulate the different forms of color blindness to see how the number disappears. They can then change the settings in the app so that the app thinks they have, say, deuteranopia, to see how the app changes the colors to make the number more distinctive. Your students who are color blind, using the app set to their form of color blindness may see the number where they hadn’t before.

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Instructions on how to use the Color Blind Pal mobile app

Install the app by downloading it from Google Play (Android) or the App Store (iOS). When it asks, give the app permission to access your camera.

If you are not color blind or color deficient:

Click on the “i” icon, then click on “Color blindness type.”

Choose one of the five “Simulate” options. Start with “Simulate deuteranomaly” (reduced sensitivity to green and the most common form of color blindness), then tap the back arrow.

At the top of the screen, you can toggle between “Inspecting Color” which names the color in the middle of the screen and “Filtering Colors.” (Play around with “Inspecting Color” first, if you’d like.)

Switch to “Filtering Colors.” Make sure “Shift” is selected at the bottom of the screen.

You are now seeing what someone with deuteranomaly sees. Use the app to look at a range of colors, especially green and orange. Compare violet and blue.

In the settings, change the “color blindness type” to “Simulate deuteranopia” (green blindness), and tap the back arrow. Look at those same colors again. How does lacking the ability to see any green (deuteranopia) compare to being green-deficient (deuteranomaly)?

Change the “color blindness type” again to simulate the other forms of color blindness: protanopia (cannot see red), protanomaly (red-deficiency), tritanopia (cannot see blue). How do colors look different when simulating deuternopia compared to protanopia?

If you are color blind or color deficient:

Click on the “i” icon, then click on “Color blindness type.”

Choose the type of color blindness that is closest to yours: protanopia (red), deuteranopia (green), or tritanopia (blue), then tap the back arrow. If you're not sure which form you have, start with deuteranopia (also covers deuteranomaly, the most common type of color blindness).

At the top of the screen, you can toggle between “Inspecting Color” which names the color in the middle of the screen and “Filtering Colors.” (Play around with “Inspecting Color” first, if you’d like.)

Switch to “Filtering Colors.” Make sure “Shift” is selected at the bottom of the screen.

The app will “shift" hues away from colors that are hard to distinguish toward colors that are easier to distinguish.”  

At the bottom of the screen, select “Filter.” Everything will appear gray except for the color you chose on the slider. How do the colors change for you? What looks different now?

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*Color blindness vs color deficiency. Technically, the only people who are color blind are those with no color vision at all. Everyone else has different degrees of color deficiency. However, color blindness is in common use to mean any degree of color deficiency, I will use color blindness in this post in that way.

References

Dubno, Z. (2019, February 5). Letter of recommendation: Color blind pal. The New York Times Magazine. Retrieved from https://www.nytimes.com/2019/02/05/magazine/letter-of-recommendation-color-blind-pal.html?partner=rs...

National Eye Institute. (2015). Facts about color blindness. Retrieved February 13, 2019, from https://nei.nih.gov/health/color_blindness/facts_about

White, P. J. T., Smith, J., & Heideman, M. (n.d.). The evolution of trichromatic vision in monkeys. Retrieved February 17, 2019, from https://lbc.msu.edu/evo-ed/pages/primates/index.html