Pretending Color Blindness – How to Uncover It

Usually people cheating on color blindness tests want to pretend, that they have normal color vision. This should give them the opportunity to get a job of their dream like police officer.

In this case it is just the other way around: Pretending to be colorblind to get the right job.

I am a doctor at US California and I have to do medical examination of the candidates for health services. How can I determine whether a candidate having normal color vision is feigning/malingering of being color deficient.

Beside the question on how to uncover someone who tries to pretend color blindness, don’t you also ask yourself why somebody would do this? I had the same question. But first I will try to give an answer on the uncovering and afterwards I will tell you the reason for malingering of suffering from a color vision deficiency.

Uncover pretended color blindness

There are different possibilities how you can check if somebody is really colorblind or does only pretend it. They all are based on the same source: A non-colorblind can’t possibly know how a colorblind sees the world.

Usually you hear about red-green or blue-yellow color blindness and you could think, that’s easy to imitate. But it isn’t at all. This colors are just the main problem colors. For example I am red-blind and I have problems in distinguishing

  • dark-red from brown or very dark-green
  • orange from a grass-green
  • yellow from a very bright-green
    but also blue-green from gray from some purple
  • any purples, violets, dark-blues
    and when is something still very dark-blue and when is it black?


You can see from this list, it is not just red and green (red-blindness is a subtype of red-green color vision deficiency) but also many other colors.

Color blindness tests

Usually you will use some kind of color blindness to detect color vision deficiency. The most precise tool would be the anomaloscope to check for red-green color blindness. With this tool it is almost impossible to lie.

 You have to fit a combination of red and green to the brightness of yellow. Answers will always lie on a straight line. So if the match is just anywhere, the test person doesn’t tell the truth.

Using some kind of arrangement test with colored discs which have to be arranged in the correct order, makes it also almost impossible to cheat. The produced arrangement will follow certain patterns. Somebody with normal color vision can’t possibly find this patterns just by arranging them in any order.

The most common case would be, that you are using some type of pseudoisochromatic plates like the Ishihara color blindness test. They are based on numbers or signs made of many colored dots. And these numbers/signs are hidden to people with certain types of color blindness.

Now what can you do, if you are using pseudoisochromatic plates to uncover pretended color vision deficiency? Here are a few ideas, which you could try out:

Show the plates in a different order. Some may have learned just the correct order and know, what they have to see and what not. If you rearrange them, you can find out more about their real color vision.


Use the mixed plates. There are plates which include a number not visible to green-blind persons and a second number not visible to red-blind persons. If somebody wants to cheat on this, they really have to know what they can see and what not.


Include plates visible only to colorblind persons. Certain shades of color are only really distinguishable if you are colorblind. So if you add some of those plates it will be hard for someone pretending to be colorblind.
Don’t use the Ishihara plates. The Ishihara color blindness test plates either containing 24 or 26 pictures are very well known. 

A candidate could learn them in advance. If you use some other pseudoisochromatic test they will struggle.
Mix in some of your own plates.

 Maybe you have the possibility to make some of your own plates with a program like Photoshop. For instance you could make some with no hidden signs and tell the person under test, that these plates have a sign which can only be seen if you are colorblind. How will they react? A person which is really colorblind, will tell your right away that he can’t see anything.

Other strategies

As I mentioned above, a non-colorblind will never know how it is to be colorblind and which colors can be distinguished and which not. Here are a few more ideas apart from the color blindness test above, which could help you.

  • Make a vision test including red letters among black ones. Ask the person under test to read the red letters. A colorblind person usually can’t easily spot red letters mixed in into black.
  • Let the person name colors. Somebody with color blindness will have problems in the whole range and mix up very typical colors. Someone with normal color vision will have problems to fake a bad color perception.
  • Ask them about everyday problems caused by their color blindness. Problems are for example skin color (has somebody a sun burn or is he sick?), cooking meat (when is it readily cooked?), LED lights (is it green, red, orange or yellow?), color charts and more.
  • Does the person have problems with traffic lights? I mean they are red and green, aren’t they. Usually this doesn’t cause real problems to somebody with a color vision deficiency. But does somebody who just pretends to be colorblind know about this?

You might try these strategies first with a few test persons—colorblind and not colorblind. This will make sure, that you have chosen the correct problem colors and situations.