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Turning this parameter on can be useful for materials that actually show complementary colors in their scattering, such as milk, which looks mostly yellow but also shows tints of blue nearer to the light source. Checking this parameter will cause the tints to be the opposite hue in the color wheel, compared to your chosen Color setting.
Vibrance
This is the actual saturation of the virtual particles inside the value that scatter the light. Higher values will make the material look much more saturated and vibrant.
Using a bright red as the main Color, the Vibrance setting was changed: 0, 15, 50, 100
Density