Plate from the Ishihara Color Test. People with normal vision will see the number 74. People with color blindness will either see the number 21 or nothing.

Testing Your Color Vision

There has been a color vision test that has been used since 1917. It was developed and published by Dr. Shinobu Ishihara. The original test included 38 color prints that were used as a tool to see if a person could not see particular colors. A person with normal color vision could see the numbers on each print. People who could not see particular colors would not be able to see the numbers, or see different numbers in the prints.

Below are some variations of the Ishihara test. The second and last test shows how the cones of the eye can become saturated.

Color Vision: Test One

Look at the pictures above. Do you see a puzzle piece in the picture on the left? If you do, you have normal color vision. The picture on the right will give you an idea of how the color picture would look to someone that is totally color blind. It is the same picture using shades of grey. Without the colors as a reference the image in the picture disappears.

It is very rare to be totally color blind. In fact, the most common form of color blindness is red/green color blindness. Approximately nine percent of the population are affected. Those that suffer from red/green color blindness (Protanopia) would see the color image above as either all red or all green. The color they see depends on which cones they are missing.

Color Vision: Test Two

If you have normal color vision, here is another interesting test. First stare at the color picture below and then move the mouse pointer on top to switch the image to the black and white version. If you look carefully you will notice the image will briefly be in the opposite color! This is because you wore-out some of your cones and are now seeing the image with whatever cones are still operating.