"Man feels himself isolated in the cosmos, because he is no longer involved in nature and has lost his emotional "unconscious identity" with natural phenomena... No voices now speek to man from stones, plants, and animals, nor does he speak to them believing they can hear. His contact with nature has gone, and with it has gone the profound emotional energy that his symbolic connection supplied." Carl Jung
This picture looks very sketchy, but it is representing the symbolism in the lighting of the play. Lots of the play is late at night or early in the morning when Stanley is playing poker with his buddies and drinking. The darkness gives the negative connotation and lets the reader know that this is more dark play than a happy and cheerful one.