Final answer:
The examples "glistening gray," "satiny sky," and "diamond drops" use alliteration.
Step-by-step explanation:
The sound device used in the examples "glistening gray," "satiny sky," and "diamond drops" is alliteration. Alliteration is the repetition of the initial consonant sound in a series of words, which creates a musical effect. In this case, the repeating initial sounds in each phrase add emphasis and create a memorable image.
Learn more about Sound devices in English literature