> These assumptions of our visual system can lead to fantastic illusions where constancy fails. Classic examples are when you see a sweater in a store under one illumination and then go outside and it's a completely different color. This is in fact the explanation for the dress illusion from a few years back -- depending on your assumption of the color of the light in the store (yellowish or whitish) the dress appears either blue and black or white and gold.

A while back I applied colour correction to that dress image. The centre image is the original, with the left and right sides being colour-corrected. The circles indicate where on the image I told Lightroom to consider neutral grey. If I recall correctly, the left side was the first point I selected, but the right hand side I had to hunt around a bit as Lightroom kept trying to go more like the left side rather than the white/gold look.