Dark
Dark colors are the realities of Gatsby's dream-like life.
The Valley of Ashes is the stark opposition to East and West Egg.
All of Gatsby's parties are held at night and are bright with a false light.

Green
Green represents a promise.
The crisp fresh grass Daisy crosses as she meets Gatsby offers a promise that turns out to be an illusion since she never commits herself to Gatsby.
Daisy's green light at the end of her dock is a goal Gatsby tries to reach but is never fully attainable.

Yellow
Yellow symbolizes the corruption and death in The Great Gatsby. Gatsby's yellow car is the murder weapon used to kill Myrtle.
The rich, flaky women at Gatsby's party swing their yellow gowns wildly as the drink and flirt and cause problems.
Dr. T. J. Eckleburg wears yellow spectacles to block America from seeing what the nation has actually become.

White
White usually symbolizes purity.
Gatsby lives in a great white mansion and wears white or pink suits, representing his innocence and pure heart.
When Nick first sees Daisy and Jordan, they are both clad in white, trying to appear pure. As Nick Learns more about Daisy and Jordan, their dresses become creamy, then yellow or gold.
A Daisy itself has pure white petals but a center, or heart of yellow. Daisy herself seems pure and innocent, but her heart is not as pure as her appearance.

Blue
Blue symbolizes romance and illusions.
Gatsby's dream-like parties are filled with blue music