Directly contradicting the classical theory that the perceived color of a surface is solely determined by the spectral composition of the light reflected by the surface (first stated by Newton), many experiments discussed above (Land's Mondrian experiments, the asymmetric color matching experiments, some of the color illusions, etc.) have shown clearly and convincingly that lights of identical spectral composition may be perceived as different colors, and, on the other hand, lights with different spectral compositions may be perceived as the same color, due to the lights from the surroundings in the space. In other words, some spatial comparison also plays a role in color perception. We have reason to believe that the perception of color seems to be composed of two levels of comparison: the comparisons between the L, M, and S retina cones followed by the spatial comparisons with some site in the retina and/or the visual cortex.
This is a good place to revisit the questions we asked before: Is color a property of the external world passively received by the visual system, or is color only in existence in our brain as a phenomenon of our perception? Now we see that the answer is definitely the latter.