(At this point art textbooks proceed directly from Newton's prism to the color wheel and pigment color mixing without equippng the artist with the simple physics of chromatic aberration behind the optical illusion that gives the artist control of color depth in art).
Sir Isaac directed sunlight through a prism lens where it dispersed into the colors of the spectrum. Each color emerged at a different angle. The lens of the eye operates under the same principal (chromatic aberration) as Sir
Isaac's prism lens.
As each color enters the eye, it bends at its preordained angle. With Newton's set of angles in mind, let's reexamine nature's set of distance angles.
As we determined, light rays from your thumb and the window entered the eye at different angles. If we examine an actual landscape, as pictured next, we find that each distance enters the eye at a different angle......and is focused by a different lens shape.
If we compare color light-rays with distance light-rays we find that:
(1) their angles are similar,
(2) both require rounding or flattening the eye lens in order to focus
onto the retina,
(3) and only one color or one distance can be focused on the
retina at a time.
Which brings us to this conclusion: Where distance angles focus nature to advance and recede visually, color angles make picture planes appear to advance and recede visually,... because, in the eye and brain, color angles mimic distance angles, and distance angles are three-dimensional!