A very well known and established type of color blindness tests are hue discrimination or arrangement tests. This type of test uses the fact that colorblind people mix up colors along the so called confusion lines.

What do you have to do? Arrange the colored squares in the correct color by picking the most similar color from the choice below. You can order them by dragging the color squares into the upper boxes. Start with the pilot, which is already set.

You should be aware of that any type of online color blindness test is very dependent on your display settings and ambient light. You should visit your local eye specialist to get a correct diagnosis. If you take the test under different conditions you will recognize that the results can vary.

The test above simulates the D-15 dichotomous test which was introduced by Farnsworth in 1947. It aims to divide people into two groups. Slightly colorblind and not colorblind people which pass the test and all others who fail it.

Colorblind people will arrange the colors not in the correct order but parallel to one of the three confusion lines: protan, deutan, and tritan. Vingrys and King-Smith developed in 1988 a scoring method based on color difference vectors. This way it is possible to quantify the type of color blindness by you personal confusion angle and the severity through the confusion index.

• Confusion Angle: The angle identifies your type of color vision deficiency. An angle above +0.7 degrees points towards a protan defect, between +0.7 and -65 a deutan defect and bellow that a tritan defect.
• Major and Minor Radius: The ratio of those two numbers results in the S-index.
• Total Error Score: Combining the two radii into a score of total error. The TES ranges from around 11 up to about 40 for strong vision deficiencies.
• Selectivity Index: This ratio shows the parallelism of the confusion vectors to your personal confusion angle. A low ratio—below 2—can either mean you have no color deficiency or you ordered the squares randomly. High numbers—up to 6 and even higher— show high parallelism.
• Confusion Index: The ratio between your major radius and the major radius of a perfect arrangement. People with normal color vision or slightly colorblind persons have a ratio below 1.2. The higher this number grows—up to above a ratio of 4—the more severe is your color blindness.

The table below shows some average results taken from a study with 120 colorblind and not colorblind people.

	Angle	Major	Minor	TES	S-index	C-index
Normal	+62.0	9.2	6.7	11.4	1.38	1.00
Protanopia	+8.8	38.8	6.6	39.4	6.16	4.20
Protanomaly	+28.3	18.0	8.2	20.4	1.97	1.95
Deuteranopia	-7.4	37.9	6.3	38.4	6.19	4.10
Deuteranomaly	-5.8	25.4	9.6	27.5	2.99	2.75
Tritan Defects	-82.8	24.0	6.4	24.9	3.94	2.60