We have all seen this actually happening in art when complementary pairs are used to make picture planes advance and recede. Delacroix wrote in his notebooks: "A man with a yellow complexion will have violet shadows, one with a reddish complexion green shadows." We understand why when we compare color angles in the eye. Green recedes from Red in the spectrum....
...and from red on the retina.
Remember that both red and green on Delacroix's painting are visible on the retina at the same time, but when red is in focus green recedes from the retina;, just like the thumb and window discussed earlier. When red is in focus on the retina, green recedes from focus on the retina by three steps.
When Delacroix paints a man with a reddish complexion he paints the shadows in green so they will recede by 3 steps of focus, giving the painted head an optical illusion of depth.
The eye lens must flatten to focus from red to green, just as it flattened to focus from your thumb to the window. The lens changes shape like this: