This occurs because some of our brains are confused by the original image’s washed-out, overexposed lighting. Our visual systems intuitively know to filter out normal backgrounds and lighting in order to see the “true” color of an object but the bluish tint to the photo is throwing off that ability for many people, thus they see gold and white.
The actual dress is black/brownish and blue.
Personally, I have seen both colors just as many others have, it is crazy but its just the brain just trying to create a definite, accurate image.