The color imagery in this passage evokes an imitative state, a falseness, as well as suggesting luxury, opulence, and Hedonism. There is, for instance, the "blue gardens" of Gatsby--blue is never a color found in gardens. Opulence is suggested in even the food turning to a "dark gold," and the hedonistic overtones emerge with the laughter that "spilled with prodigality."
More yellow imagery--suggestive of corruption and artificiality--appears with the "yellow cocktail music" that is surrounded by the chatter of men and women who do not even know each others' names. The artifical lights grow brighter as the "earth lurches away from the sun" and real light.