Why would a green snake be better able to survive and reproduce in an environment of tall green grass than a brown snake would?

A green snake would likely have a better chance of survival because the color of his scales blends in with the tall green grass. Not to mention that the grass is tall and it would be hard to spot the snake.

Since the green snake would be in an environment with tall green grass, it would blend in better and the other snakes would likely be it species, while the black snake would not blend in with the grass and would likely be a different species than the rest of the snakes therefore not being able to reproduce as easily.