What “Gatsby believed in the green light, the orgastic future that…” means
Gatsby believed in the green light, the orgastic future that year by year recedes before us.
— Nick Carraway, The Great Gatsby · F. Scott Fitzgerald
The green light at the end of Daisy's dock is Gatsby's whole hope made into a color. Fitzgerald names the tragedy of the dream directly: the future we believe in keeps moving further away the harder we reach for it.