A prism is a transparent piece of glass or plastic that is cut with multiple smooth sides to refract light. Since a prism has multiple sides, anything described as prismatic is also being described as being multifaceted. In addition, since a prism refracts light, it absorbs light and breaks it up into every color of the rainbow. Therefore prismatic can also be used to describe something as very colorful, meaning very diverse.
Shakespeare shows us that love is prismatic, or multifaceted by showing us that there is just as much a painful side to love as there is a beautiful side. We especially see the painful side of love in the very first scene when Romeo wails over being rejected by Rosaline. In fact, Romeo best portrays the multifaceted nature of love through his string of oxymora describing love:
O brawling love! O loving hate!
O heavy lightness! serous vanity!
Misshapen chaos of well-seeming forms! (I.i.174-77)
This string of oxymora shows us that love appears in two forms: in the form of something sweet and wonderful and also in the form of something horrible, like hatred.
Two other sides to love that Shakespeare portrays are its intense, passionate side plus the more real side of love that's governed by reason. We see the intense, passionate side of love when Romeo and Juliet both fall in love at first sight. In fact, Romeo's love is really more of an intense physical attraction, which he confesses to in the lines, "Did my heart love till now? / Forswear it, sight! / For I ne'er saw true beauty till this night" (I.v.54-55). However, intense, passionate physical attraction is not the realist side of love. The real side of love requires the rational mind. Real love is a choice to love a person, even though that person possesses both good and bad traits. We see this side of love exhibited when Juliet is faced with making a conscious decision to either hate Romeo or continue loving and trusting him even though he has just killed her cousin Tybalt. Juliet exhibits the real side of love when she makes the choice to continue loving and honoring Romeo because he is her husband and reasons that he must have killed Tybalt out of self-defense.
Since love has so many sides, not only can we say it is prismatic through being multifaceted, but we can say that love is very colorful, meaning very diverse, which is another attribute of being prismatic.