GREEN

Green is a mixture of the colors blue and yellow; it represents Gatsby's dreams and his wealth hopelessly tangled together. There is a green light at the end of Daisy's dock, which suggests Gatsby has kept his dream of the Daisy he knew and loved before he made his fortune, and the fact that their relationship will always be affected by money.
Green is also traditionally represents spring or a new beginning. Gatsby sees the green light as hope for a relationship with Daisy.
Also, in the end, Nick associates Gatsby's dream and the green light to the American dream, "a green breast of new land" (189) where people could come to start over.