Japanese vision expert Kazunori Asada suggests that Dutch painter Vincent van Gogh, famous for his richly colourful post-Impressionist paintings, may in fact have been colour blind. Asada came to this conclusion after viewing van Gogh's paintings under light filtered to simulate how the world looks to someone with colour blindness.

While visiting the "Colour Vision Experience Room" at the Hokkaido Color Universal Design Organization (HCUDO), during an event intended to educate the public about the diversity of colour vision which exists in our society, Asada noticed something unusual when viewing paintings by van Gogh.

"This painter has a somewhat strange way to use colour. Although the use of colour is rich, lines of different colours run concurrently, or a point of different colour suddenly appears. I’ve heard it conjectured that van Gogh had colour vision deficiency," Asada wrote in a blog post.

"However, in the van Gogh images seen in the Colour Vision Experience Room, to me the incongruity of colour and roughness of line had quietly disappeared. And each picture had changed into one of brilliance with very delicate lines and shades. This was truly wonderful experience."

In other words, the works appeared the same - if not better - when viewed under the filtered light.

To explore his hunch about van Gogh's colour blindness, Asada developed a mobile app called the Chromatic Vision Simulator which shows what images look like for people with one or more defective sets of cones, the structures in the eye used to see colour.

You can see a side-by-side comparison of an original and a protanomal simulation of van Gogh's painting "Starry Night" below ("protanomal" refers to those who cannot distinguish between green and red), and find many more examples on Asada's blog.

The Chromatic Vision Simulator supports "Normal Color Vision," "Protanope," "Deuteranope" and "Tritanope" colour deficient types, and is available for iOS and Android devices. You can download it for free, find out more here.