"…you’ll notice you see a dark brown tile at the top, and a bright orange tile at the side. That is your perceptual reality. The physical reality is that those two tiles are the same."
After the audience cannot detect the color of dots on black and white backgrounds:
"…nearly every living system has evolved the ability to detect light in one way or another. So, for us, seeing color is one of the simplest things the brain does. And yet, even at this most fundamental level, context is everything."
As his TED bio says:
Beau Lotto is founder of Lottolab, a hybrid art studio and science lab. With glowing, interactive sculpture – and good, old-fashioned peer-reviewed research – he’s illuminating the mysteries of the brain’s visual system.
A tip of the eyeball to Book of Joe, where I first discovered this.