Euro Coins—A Simple Color Blindness Test

Did you ever wanted to quickly make a color vision test with one of your friends? Put a few euro coins into your pocket and you will always have a simple color blindness test handy and ready to use.

Euro Coins Color Blindness Test
Euro Coins Color Blindness Test — (left) normal vision,
(center) deuteranope simulation, (right) protanope simulation

P. J. Pardo, A. L. Pérez and M. I. Suero, three researchers from the University of Extremadura, Spain, found this simple test while looking for an uncomplicated possibility to test for color vision deficiency. The discovered that there are two different classes of coins:

  • 1, 2, 5 cent coins made of copper-covered steel with a reddish tone.
  • 10, 20, 50 cent coins made of Nordic gold with a yellowish tone.

Measuring the exact colors and calculating the coordinates in the CIE color space showed, that the two different colors are arranged on the deutan confusion line. This means that green-blind people wont be able to distinguish the colors and also red-blind people will have significant problems. So they found a simple possibility to test for red-green color blindness

So this are the facts. And now, how can you perform a color vision deficiency test based on this findings?

  1. Gather 5 coins each from lower and upper values. Use coins from different countries, as they have different back sides.
  2. Mix them and show the coins with the value side facing down to your friend.
  3. Ask your friend to sort all the coins based on their colors.
  4. See how your friend performs on the task.
  5. Explain the facts why this is a valid red-green color blindness test.

Any person with normal color vision should be able to sort them quickly and of course correct. Red-green colorblind people will have more or less problems to sort them and often try to sort them based on brightness. If you try this test on several persons (including colorblind people) you will recognize the difference.

For more details on this test see Euro: A new color vision test in the pockets of three hundred million Europeans.

Happy testing! — Check the color vision abilities of your friends and your family with this simple color blindness test. It would be great to hear some of your experiences. If you like, share them in the comments.

8 responses on “Euro Coins—A Simple Color Blindness Test

  1. susan

    Is there a test for a violet-blind person? I understand it is a rare form of color-blindness.

  2. Karen

    Susan, your comment is interesting because I didn’t know there was a “violet-blind” name for any of the types of color blindness. I apparently have trouble seeing violets, sometimes see certain greens as blues. I learned this only a while back when I got into an argument about a dress color…. :)

  3. David

    Protanopia and deutoranopia are sex recessive traits linked to the X chromosome and cannot happen at the same time on men. Women can have X (normal), Xr (protanopia) and Xg (deuteranopia), so the following combinations could happen XX (normal), XrX and XgX (normal vision but carrier), XrXr and XgXg (protanopia or deuteranopia vision) and finally XrXg (tetranopia) which is under investigation ^^.

    Tritanopia (blue-green colorblindeness) is not linked with the X chromosome and happens in very rare cases. In even rarer cases it can appear in combination with protanopia and deutoranopia.

    That may change your confusion lines.

    My parents are from a region where mild tritanopia is common and as result it seems that I have both mild blue-green blindness and strong deuteranomaly.

  4. Emmanuel

    I don’t see any difference between the second and third pair of coins. Should I?