Donald D. Hoffman writes:
On the left are 49 colored patches. On the right I have randomly shuffled these same 49 colored patches. This dramatically affects the colored surfaces and lights that you see. On the left you see colored lights shining on the patches, e.g., a bright yellow light shining from the lower left and a bright green shining from the upper left. On the right you see the patches as illuminated by a single achromatic light source. You also see on the right some tans and browns that you don’t see on the left. In fact the patches on the right might appear so different from those on the left that you might not be able to figure out the proper matches between them. I’ve indicated two of the matching pairs by the numbers 1 and 2.