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.

Optometry experts are calling the photo a one-in-a-million shot that perfectly captures how people's brains perceive color and contrast in dramatically different ways.

Those who subconsciously seek detail in the dress' many horizontal black lines convert them to a golden hue, while the blue disappears into a blown-out white. Experts say the photo's exceptionally warm yellow backlighting triggers this alternative perception.

The English dress retailer, Roman Originals, has reported a million hits on its sales site since the photo's worldwide distribution Thursday night.