Friar Laurence's first spoken speech certainly is a long series of contrasts, especially contrasting images. As we are limited to space, below are a few ideas to help get you started.
Images are words that conjure up "mental pictures" for the reader (Dr. Wheeler, "Literary Terms and Definitions"). Since they conjure up mental pictures, they are words that relate to the five senses, touch, sight, sound, smell, and taste. Focusing on contrasting images to begin with will certainly make things a little easier. We can begin to see the contrasting images even in the first four lines:
The grey-ey'd morn smiles on the frowning night,
Check'ring the Eastern clouds with streaks of light;
And flecked darkness like a drunkard reels
From forth day's path and Titan's fiery wheels. (II.iii.1-4)
Both "smiles" and "frowning" are facial expressions we can see and, therefore, sight images. Plus, they are opposing sight images. Since we associate smiling with happiness and frowning with sorrows or troubles, we know that "smiles" has a positive connotation while "frowning" has a negative connotation. In addition, the image "morn," meaning morning contrasts with the image of "night." Both are sight images as well because we can see morning and night. Morning, or light, is often associated with goodness and has positive connotations, while "night" is often associated with darkness or evil and has negative connotations. We can see the exact same thing in the word "darkness" and the phrase "Titan's fiery wheels." The phrase "Titan's fiery wheels" refers to the Roman myth of the god Apollo. Apollo, the sun god, was believed to drive the sun across the sky each day with his chariot, being responsible for both the rising of the sun and the setting of the sun. Hence, "Titan's fiery wheel" again refers the image of morning, which contrasts with the image of darkness.