Lady Macbeth provides a rather lengthy example of darkness imagery in Act 1, Scene 5. She says,
Come, thick night,
And pall thee in the dunnest smoke of hell,
That my keen knife see not the wound it makes,
Nor heaven peep through the blanket of the dark
To cry, "Hold, hold!" (1.5.57-61)
She addresses the night directly, referring to its darkness as "thick" because it is so complete; she asks the night to cover up everything with hellish smoke, the darkest ("dunnest") smoke, so that her knife will not be able to see the wound it creates and so heaven won't be able to see through the blanket of darkness and object to her actions. Not only do these lines include visual imagery of darkness and how incredibly black Lady Macbeth wants that darkness to be, but she also uses apostrophe when she directly addresses the night as though it could hear and respond. In addition, she personifies her knife, giving it the ability to see, and she personifies heaven as well, giving it the ability to both see and speak.
Later, in Act 3, Scene 1, Banquo says,
Go not my horse the better,
I must become a borrower of the night
For a dark hour or twain.
Here, he is answering Macbeth's questions, and he means that he will have to ride an hour or two after darkness has fallen. Obviously, this kind of imagery is visual as well since Banquo discusses the darkness.
Just prior to Macbeth's failed dinner party, he speaks privately with his wife. He has already planned Banquo's murder though he doesn't tell her about it. Instead, he says,
Come, seeling night,
Scarf up the tender eye of pitiful day
And with thy bloody and invisible hand
Cancel and tear to pieces that great bond
Which keeps me pale. Light thickens, and the crow
Makes wing to th' rooky wood (3.3.52-57)
Like his wife in Act 1, Macbeth now directly addresses the night (using apostrophe), asking it to come and seem to place a scarf over day's eyes (like a blindfold); he personifies both night and day then. He also wants night to use its bloody and invisible (perhaps because it is dark and such bloody deeds cannot be seen) hand to separate Banquo from his life. He also describes the coming night as a "thicken[ing]" of the light.
When Macbeth visits the Weird Sisters after the dinner party, he calls them
secret, black, and midnight hags [.] (4.1.48)
He refers to the witches in this way in order to emphasize his belief that they are, indeed, dark of purpose and associated with night (which he's already made clear he associates with bloody deeds).