In Act III scene V of Romeo and Juliet, Shakespeare uses much chiaroscuro, an "effect of contrasted light and shadow." Using two different outlooks on their future, Romeo and Juliet juxtapose each other in terms of imagery.
After their first and only night together, Romeo is fearful of being caught and killed:
Juliet refutes him, wanting him to stay:
So, darkness imagery connotes death, while light imagery connotes hope. Later, however, the two will switch positions.
This means that the lighter and lighter it gets the darker and darker their future is. Since their marriage is a secret, they must meet each other at night. In the full light of day they will be discovered.
Juliet finally tells Romeo:
She uses contrasting dark and light imagery to foretell Romeo's death. She foreshadows the ending in the Capulet family tomb, except that it will be Romeo who will find Juliet. So, while Romeo used the darker, morbid imagery at the beginning of the scene, it is Juliet who ends with it.