Final answer:
Macbeth and Lady Macbeth both refer to 'darkness' to conceal their evil intentions, reflecting their moral corruption and setting a scary tone in the play.
Step-by-step explanation:
In William Shakespeare's Macbeth, both Macbeth and Lady Macbeth use the imagery of darkness as a way to express their wicked intentions and desires for power. This darkness is symbolically associated with the evil acts they are planning to commit. As they both wish to conceal their deeds from the eyes of others and their own consciences, darkness becomes an important motif representing their wish to operate unseen, reflecting their inner moral darkness and contributing to the scary tone of the play.