<spoilers>
Sour Cherry is a long and odd retelling of the Bluebeard story that is also a reflection on domestic violence generally. For most of the novel we are led to believe that the teller is in the tale being told, at the end of the line of dead wives, but this is not so. In the final pages, it becomes clear that she is a woman, mortally wounded by her domestic partner, telling the tale to her son while waiting for the police to arrive.
The word "blue" appears 40 times in the novel, and several of these instances it is used in reference to hair.
The first time it's used to describe hair is shortly after Agnes arrives to wet nurse the infant who will become Bluebeard (page 10). In this case, it describes the father:
His hair was curly and the same black as the child's, so dark that when it caught the light just right, it took on the most beautiful blue tint.
The next time (page 60) it describes the child being told the story:
Your hair has gotten so long, blue-black curls down to your shoulders. When did it get so long? How did I not notice?
Finally, at the beginning of Tristan's chapter (page 98) it's used to describe a beard:
Tristan's father was large, his voice booming and all-encompassing, the curls of his beard so dark that, when the light was just right, they seemed blue.
Tristan's father is Bluebeard, and his beard is once again described (page 147) shortly before he kills Tristan:
The man patted the mare's flank tenderly. The moonlight fell on his face in such a way it made his beard look blue.
On page 160 the Bluebeard story is explicitly referred to as one that Agnes tells Eunice (Tristan's mother). After Eunice dies and Bluebeard takes a second wife (page 181):
He turned her away sometimes, taken by one of his dark moods that made his hair look blue.
After the wives are dead and Bluebeard meets his Cherry Girl (page 220):
The fabric he wore made a dry, rustling sound as he moved into the room. It was black, something with hair, and his beard was gathered beneath his chin, so dark it appeared blue in the evening light.
At the end (page 282)
I've always known how it ends, even though my man's beard is not blue at all.
Some characters, like the boy being told the story and his mother telling the story and her man who kills her, are never named. Others, like Bluebeard himself and his father, are named, I think?, but I have forgotten them. This is perhaps a reason for the length of the novel, so that this man's name is washed away in a tide of words. Meanwhile I do remember Agnes, and Tristan, and Eunice, though Agnes is referred to as "Cook" for most of the novel.
