Illusion of DEPTH
Vision, like all other senses, evolved to help us survive.
In reality, there is nothing like "light." Electromagnetic waves, emitted by energy sources or reflected from materials, activate cell proteins in our eyes, and our brain "sees" things.
Different types of cells understand specific colors (hues) and aggregated light (tints or shades), and the signal is conveyed to areas of the brain to make sense of it.
The uneven distribution of these cells in different areas of the retina is part of the evolution of the eye and eyesight. The way we interpret patches of different hues enables visual artists to evoke specific feelings and provide the impression of depth. The rectangular block shown is an example. The three columns of identical patches interact with the gradient background and present themselves differently. It's easy to notice how these rectangles 'feel' different from top to bottom. In this case, our brain's color processor confuses the color with darkness and distance (push-pull colors).
I use such illusory compositions to reflect the mood of a painting.