The answer is simple. Here’s Nick Taylor-Vaisey’s one-sentence explainer
Debbie Armstrong adjusts a two-tone dress in a window display of a shop in Lichfield, England. It’s the dress that’s beating the Internet black and blue. Or should that be gold and white? Friends and co-workers worldwide are debating the true hues of a royal blue dress with black lace that, to many an eye, transforms in one photograph into gold and white. (AP Photo/Rui Vieira)
The dress looks different because your eyes process colour differently than some other people’s eyes.