One of the most often repeated image patterns in Romeo and Juliet involves the interplay of light and darkness. For example, Romeo compares Juliet to light throughout the play. Upon first sight of her, Romeo exclaims that she teaches "the torches to burn bright" (I.5.43). She's also "the sun" who can "kill the envious moon" (II.2.3). Later in the same scene he claims that her eyes are like "[t]wo of the fairest stars in all the heaven" (II.2.15). But Juliet's light shows best against the darkness; she "hangs upon the cheek of night / As a rich jewel in an Ethiop's ear" (I.5.44-45).
Juliet also associates Romeo with a light that illuminates the darkness. If Juliet dies, she wants Romeo "cut in little stars / And he will make the face of heaven so fine / That all the world will be in love with night, / And pay no worship to the garish sun" (III.2.22-25). This quotation reminds us that Romeo and Juliet's light shines most brightly in the dark -- it is a muted glow associated primarily with stars, torches, and the dawn, rather than with sunlight, which is almost obscenely bright.
Like the darkness, their love is associated with mystery, emotion, and imagination. In fact, the day works against them. At the end of their honeymoon night, Romeo says, "More light and light: more dark and dark our woes" (III.5.36). The lovers must part before the light arrives to ensure that Romeo isn't caught and killed.