Symbolism, Imagery, Allegory
There Will Be Blood
The Grapes of Wrath is full of the red stuff. Consider the slaughtering of the pigs, the way Tom cuts his hand fixing the touring car (and then uses his urine to make it stop bleeding—ew), the Joad dog that gets run over, the farmland that is being bled dry by drought and by cotton, Rose of Sharon's baby's birth, and more.
We also know that the "grapes of wrath" in "The Battle Hymn of the Republic" refers to injustice and spilt blood. Blood signals both life and death, so let's pay attention to moments in which it bubbles to the surface of this novel.