Blue: related to Gatsby and his dream, numerous times Gatsbys party is described as having a romantic blue aura around them. When Gatsby is with Daisy its a perfect blend of blue and white that blissfully make the area feel like a dream. Blue seems to represent success in this novel too because when Gatsby starts his new life with Dan Cody the first thing he buys is a blue coat. However, like most good things in this novel, once the party is over or Daisy leaves Gatsby; thats when the mysterious yellow haze takes over the blue.
Red: related to Gatsby and Nick, with Gatsby it symbolizes strongly the ugliness of reality and the masquerade of success. With Nick, it illustrated the dazzling world of the rich and the enchantment of material riches. However as the novel progresses red becomes grotesque and is related to violence and death.
Yellow: related to money and wealth. This is the most widely used color in the novel; its usually used in conjunction with a demotion of something being gold to just plain yellow. A great example of this is Gatsbys car, before it kills Myrtle its a pristine cream colored car however, after the murder it loses its luster and become a yellow car.
Green: related to Daisy and encouragement of Gatsby, beckoned Gatsby to make Nick invite Daisy over so they could meet. However, Gatsby seeking the blue and green hue disregards the yellow that creeps in and ultimately leads to his tragic downfall.