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.

If a Women is a Carrier of Color Blindness does she also Suffer from it?

Many people think that only men can be colorblind. As we can learn from genetics, this is not true. There are a lot more men colorblind, but also women can suffer from a color vision deficiency.

Here’s a question for experts: according to a vision test in a magazine she did recently, my mother has a slight red-green weakness, which, however, is hardly noticeable in daily life. Is this also colour blindness, although that is really rare in women, and it’s nothing compared to her father’s colour blindness, which was pretty severe? Or can it be due to her being a carrier?

On a first glance it looks like we can give a quick and short answer on this. But thinking about it, makes it a bit more complicated.

First of all, yes women can be colorblind and even if it is a very weak form of it you call it color vision deficiency (a wording which reflects much better the fact that colorblind people can also see colors). And it doesn’t matter if it is rare or not.

Sex chromosome X encodes color vision.
XY = man
XX = woman.

Now let’s have a closer look at this case. We have a colorblind man which means he has a defective X chromosome which pairs with a Y. The Y chromosomes have no coding of color vision and therefore have no important role here. His daughter will inherit this defective X and another X from her mother. We have now to possibilities:

  1. The mothers X is also defective concerning color vision.
  2. The daughter inherited an X encoding perfect color vision.

In the first case the daughter definitely shows some form of color blindness which she inherited from both of her parents. It is said that the weaker form either from her father or from her mother would control her color vision.

X-linked recessive carrier mother

According to genetics the daughter shouldn’t be colorblind in the second case. But it is known from different cases that this isn’t always so easy to tell. Up to now it is not fully understood how those two X chromosomes affect the color vision system. It could be very well that both of them play their part in the setup of the color receptors. In this case the strong color blindness encoded on her fathers X chromosome could also affect the color vision to a certain degree.

Putting this together means, that the daughter can show characteristics of color vision deficiency in the first and the second case. Only a detailed genetic analysis could tell us more details about it.