Final answer:
The phrases "happy in the hour" and "rainbow light" support the use of symbolism in Amy Lowell's poem "Song".
Step-by-step explanation:
The literary element supported by phrases like "happy in the hour" and "rainbow light" in Amy Lowell's poem "Song" is symbolism. Symbolism is the use of objects, colors, and concepts to represent abstract ideas and emotions. In this case, the phrases mentioned evoke feelings of joy, happiness, and beauty, symbolizing the positive aspects of life and the transformative power of love.
Learn more about symbolism in Amy Lowell's poem "Song"