Many visualization projects use colour schemes to help viewers visually understand and distinguish complex data sets and information. But have you ever thought about the fact that people who are visually impaired have trouble viewing them? How could you read and appreciate a map that is not readable? Possibly as much as trying to read a map in a language you don’t speak. Now there is an app to help people with colour blindness and other visual impairments to better read the London Tube map called Colourblind Tube Map.