Answer: 2. Tone
Explanation: The figure of speech tone refers to the author's sentiments or feelings about the characters or the story he is writing, in this case the author uses a metaphor ("running together and combining like a fresh watercolor painting left out in the rain") to express her feelings about some memories.
Also it can't be any of the other options because setting refers to the place and time the story is developed, conflict is the main problem of the plot, and theme is the learning we get from the story.
