Well, I've checked out the scene in question, and came up with a similar conclusion.  On the one hand, the color is definitely intended to be kaleidoscopic, since Giuliana even says something to the effect of "I hate the factories, the colors, the people...".  On the other hand, there is a stark variation in brightness, not just on the unfiltered shots, but also within the same hues.  The varying shades of amber were also particularly noticeable.  The fact that she had to look out of the window at night (to see the man in the street) also supports the idea that they shot the scenes out of sequence, most likely during daylight hours, to work around the nighttime window shot.

So I tend to agree that the color saturation is relevant, although the variation in light seems to be a continuity problem.

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