In this passage from Shakespeare's "Macbeth," the character grapples with the overwhelming guilt and horror of their actions. The imagery of blood symbolizes not just the physical act of murder but also the deep-seated remorse that taints the character’s soul. The reference to Neptune’s ocean suggests that no amount of water can cleanse them of their guilt, as their guilt is so profound that it would turn the very seas red with their blood.

Additionally, there's a sense of shame expressed when comparing their hands, which are stained with blood, to those of a more innocent character. While one character voices the simplicity with which a little water can wash away their sins, the other understands that this act cannot truly erase the psychological burden. This highlights the theme of guilt and the irreversibility of their actions, as the weight of their deeds profoundly affects their conscience.