In both comparisons, the beloved person, as well as the affection towards they, has to do with emotions. Talking about a red rose that is fresh, lovable and that represents love, more specifically passionate, deep and intense love. The poem also says many times the word red, which is used to emphasize the intense emotions.
The second comparison about a melody makes reference to how beautiful peaceful and at the same time passionate and harmonious a melody can be, just the way the speaker and they beloved interact in their connection
Inference is often difficult for students to understand initially, especially for younger students. It can often slip just beyond their grasp due to its subtle nature.
