Health beat: Before #TheDress there was #TheCoat

When Dr. Erik van Kuijk traveled to London, the University of Minnesota ophthalmologist called a clothier and ordered a sports jacket that was deep British blue.

When he arrived for pickup, the coat sure looked black.

"No, no, no," he was told. "This is true navy blue."

Until Van Kuijk looked at it in the light of day back home.

"Let me tell you," he said, "that thing is black."

Let's just call it #TheCoat — a reminder that color debates have been taking place in some way, shape, form or garment since long before #TheDress.

But regarding last week's social media phenomenon — in which a photo divided the world over whether a party dress was gold and white, or blue and black — Van Kuijk and colleagues said there is fascinating science behind it.

It's unclear whether the resulting variations reflect physical differences in people's retinas — such as the share of cone cells that interpret color vs. rod cells that interpret contrast — or also life experiences that train brains to interpret complex color situations differently.

But it's clear that a stop sign might appear a different hue of red to different people, especially as the lighting changes, said Dr. Erick Bothun, another U ophthalmologist.

The overexposed dress picture is tricky, because it zooms in on the dress and gives few clues to the bright surrounding light that illuminates it. So individuals' brains are making unique interpretations about the actual color and whether light is distorting it, Bothun said. "Our brains can play tricks on us based on the assumptions they are making."

Colorblindness affects less than one in 10 people. And as the elderly develop cataracts — the clouding of the eye's lens — they have trouble with contrast and differentiating shades of gray, or dark blue from black.

Van Kuijk figures that is what happened with the salesman and his jacket color.