F. Scott Fitzgerald offered many symbolic images in his work. Gatsby is one of the most recognized literary characters ever. I think we can all see a little of ourselves in some of the characters in The Great Gatsby.
The literal meaning for the green light relates to boating. We find out that the green light stands on Daisy's dock. It was customary for green lights to be installed at the end of docks so nighttime boaters could easily find their moorings. Finding one's moorings in life is the first symbolic meaning for the green light.
The other symbolic meanings for the green light could be many. First, a green light means the go ahead. It is the color of hope. Gatsby stared at this green light throughout the entire novel.
Green can also mean the color of money and envy. We know that Gatsby was a poor man when he and Daisy first met. He knew she would not marry him, because he was poor, so he left to earn the money he thought he would need. In the meantime, however, Daisy marries Tom.
The text you gave, tells us that Gatsby had earned the money and wanted another chance with Daisy, but it also tells us that his chance is forever gone. He lives in the past, and wants what he thinks was lost to him, but realizes that the past is just that, the past. He can't win Daisy back, his money can't make her love him enough to leave Tom.
Gatsby is such a tragic character. His love of money and of Daisy, prove to be his undoing in the end. The green light he stared at, was his hope, because he always believed in the green light.