There is no white in that dress. This is what's scaring me, I had no idea how many people have such a distorted perception of color. There's a lot of talk about optical illusions and how surrounding colors alter your perception, but the objective truth of the matter is that the colors in the photo are approximately periwinkle and gold. Everyone's viewing the same image, i.e. a file containing numerical values which represent pixel colors. And you can use a small program like ColorPix to hover your mouse over the pixels in the image and read their values. I did this, and the actual colors of the pixels are exactly as I perceive them. Periwinkle is like a light blue/purple.
So what's scaring me is how many people see that periwinkle color as white. I can't for the life of me work out how anyone could get it so wrong, unless they have some severe form of color blindness. I mean there's a clear example of white in the photo for comparison - the blown out top right corner. That's white! How can anyone think the blue-purple color in the dress is anywhere near that color? It's astounding. Like a lot of people have pointed out, the color of the dress doesn't matter in the slightest in the grand scheme of things. What matters is how this has exposed the extent to which some people aren't seeing in true color. I'm shocked! When a witness to a crime says the perp was wearing a white t-shirt, to what extent are we supposed to believe them after this?