Classic moment! Captures the film's essence

I know this is an old post, but I wanted to mention how the background and lighting focus attention on the film's themes.

As Nathan and Kyoko dance, we see red and blue lights in the background. The red affirms a sense of passion and passive aggression on Nathan's part, while the blue still attempts to maintain a level of calm. The emotions you mention are perfectly captured with the color schematic.

The shirt Caleb is wearing has lost its bluish luster, and is now presented as a bluish grey, indicating a questioning of morality. Nathan is wearing black, indicating a moral emptiness as well as an ostensible patriarchy, whereas Kyoko's black underwear is highlighting an overthrow of order. Her white shirt, the absence of color, also presents Kyoko as a tabula rasa, or something to be programmed. She is absent meaning until Nathan gives her meaning. In this case, as an object.

The Jackson Pollock inspired painting behind Caleb further accentuates the message that the old is gone—this is the new; the postmodern, as it were.

While the red emphasizes the repressed anger (Kyoko later killing Nathan), the blue still confronts the audience with a sense of comfort provided by technology's ability to streamline life, and thereby diminish its redundancies (Kyoko fulfilling her function).