16/03/2026
Colour vision tests π
In 1875, following a serious train crash in Sweden which was deemed to be the result of the driver not seeing the signal colour correctly, the King of Sweden requested a formal test be developed to measure ability to see colour.
The result was the Holmgren Wool Test, where the patient was asked to find all wool samples which matched a reference skein shown by the clinician.
It has since been replaced by quicker and more sensitive tests but as you can see with these images, it still appears different with various colour vision defects.
Image 1: Full-spectrum human colour vision
Image 2: Red-green colour deficiency π₯π©
Image 3: Blue-yellow colour deficiency π¦π¨