In 2015, a photograph of a dress went viral, dividing viewers over whether its colors were blue and black or white and gold. This optical illusion highlighted differences in human color Why is it so hard for people to see black and blue?' Salvation Army uses 'The Dress' to talk about domestic abuse Orange County Register White and gold or blue and black what colour is the dress? An eyewitness gives a definitive answer The Independent The Independent Optical illusion renews blue and black dress debate nine years on Express.co.uk