A viral debate on social media , which began Thursday night, continued Friday about whether a dress worn recently to a Scottish wedding was actually blue and black or white and gold. From this day on, the world will be divided into two people: blue and black, or white and gold. A post shared by Ellen theellenshow on. He naturally saw the dress as blue and black. The optical illusion, he said, is explained by looking at graphs of the photoreceptor absorption spectra , which shows how the eye perceives colour. If light skews in one direction, a colour looks blue-black. In another, it looks yellow-white.