There are so many examples to choose from. Here are three.
Narcissus, a beautiful boy, is pursued by the nymph Echo, and he rejects her. All that is left of her is her voice after she spends day after day pining away for him. Then Nemesis, the goddess of vengeance, made Narcissus fall in love with his reflection in a pool. Narcissus couldn't stop looking at himself, and he pined away as well. In place of his body, mourners found a flower "with a yellow center surrounded with white petals".
Daphne becomes the innocent victim of a contest between Apollo and Cupid. Cupid shoots Apollo with one arrow making him want Daphne, but he shoots Daphne with another arrow that drives love away. When Apollo attacks her, Daphne asks the gods for help, and they turn her into a laurel tree.
Apollo's bird, the raven, used to be white. The raven told Apollo that he saw Coronis, a girl Apollo had seduced, with someone else. Apollo shot her with an arrow, and she then told him she was pregnant with his child. Apollo rescued the child, but he hated the raven for telling him, so he turned the raven black.