[jvidjejnsjcj]

There're two claims of fact (as opposed to just my opinion) in my comment: That layering multiple increasingly sized box-shadows in a line isn't more physically accurate than a single box-shadow, and that black is the most physically accurate color to blend with.

I'm quite confident of the first claim. You're contest of my second claim makes me think I was unclear. I don't suggest using black at 100% opacity as a shadow color. Instead, The shadow should be black with some fractional opacity, so that the background color is blended with black. The result of blending with black will not be pure black, but instead a good approximation of less intense light of the same color.

I also recognize that it's true that designers often use more saturated colors as the colors get darker, to good effect. But in the case of the shadows presented in the FA, I don't think it looks good, and whether it looks good or not, to claim it's inspired by physical realism is wrong.

[spyhi]

Fractional opacity mixing with pure black is still not the most physically accurate shadow, because in the real world ambient light is mixed in with shadow, and also the color of the object casting shadow (and the surface the shadow is cast on) also creates color casts on a second light bounce from off-angle ambient light hitting an object, which influences shadow color in a way that's not "black on top of surface color." The algorithm for blending drop shadows doesn't take these things into account. https://willkempartschool.com/the-secret-to-painting-realist...

The link above also has an example of the use of multiple shadows to create a more naturalistic feel, namely that in the real world we are accustomed to, one source of light creates multiple kinds of shadows because of reflections from clouds, objects, etc.

This is all linked to physical realism, to help carry over our expectations of what the world looks like into a (in this case) digital space.