Why, it stood by her: she has light by her continually; 'tis her command. (Act V, Scene 1)
Once again the idea of her needing to have a light at all times represented that she needed a sense of goodness to protect her from being consumed by evil. There is a shift from her calling the evil, dark forces at the beginning of the play to having to have light at all times to protect her. The two contrasting concepts became so important in showcasing the rise and deterioration of Lady Macbeth. Blood imagery was also a huge part of the gruesome play, and it would only make sense to find creative ways of describing a subject that kept showing up scene after scene. When Lady Macbeth was seen sleep walking on the fifth scene, she vividly described the smell of the stains of blood in her hands.
Here's the smell of the blood still: all the perfumes of Arabia will not sweeten this little hand. Oh, oh, oh! (Act V, Scene 1)
She talked about how not even “all the perfumes of Arabia” could make the smell of blood from all the crimes committed disappear from her body. This gave a sense of how emotionally destroy Lady Macbeth was at that point since she could still smell the strong scent of blood from her past