In Shakespeare's Macbeth, guilt is represented by the presence or symbol of blood. Macbeth, after going back and forth on whether or not to kill Duncan, eventually decides to do it. Very quickly after his murder, Macbeth feels guilty, especially when he looks down at his hands. He questions whether or not he will ever be able to wash away the blood (guilt). "Will all great Neptune's ocean wash this blood/Clean from my hand?"
Interestingly, Lady Macbeth feels no such guilt or remorse . . . at first. Her guilt is also symbolized through her visions of blood on her hands and clothes. "Out, damned spot!" She keeps imagining blood on her hands and her guilt is driving her crazy. "Yet who would have thought the old man to have had so much blood in him."
While Lady Macbeth's guilt increases as the play progresses, Macbeth's gets less and less. It must since he basically begins killing anybody that stands in his way. He even kills his own friend Banquo. Even then, though, the blood/guilt motif is set before the reader again with the line "blood will have blood."