In the book Sarny: A Life Remembered, when and why does Lucy stop hating white people?
I believe that Lucy stops hating white people gradually. When freedom first comes, and she and Sarny are on the road, they come upon a battle between Union and Confederate soldiers. Lucy waits, and "her eyes (are) shining" with anticipation. She says,
"They're all white, ain't they? I hope they all kill each other. Wouldn't bother me if every damn one of them died."
Lucy mood is quickly subdued, however, first when Sarny points out the the soldiers dressed in blue are fighting to make her free, and second, when she sees the brutality of the battle and its aftermath. As she looks upon the torn and shattered bodies, her smile is gone, and she says,
"Freedom sure costs a heap, don't it?"
As she and Sarny walk on, Lucy's eyes are filled with tears. She has just come to consider the possibility that all white people are not bad like the overseer Waller back at the plantation.
Soon after this incident, Lucy and Sarny come upon the mutilated remains of a white family, and a whimpering little white boy they name Tyler Two. Lucy is reluctant to take the child at first because he is white, but Sarny sees no other recourse for the little boy. It is not long before Lucy becomes attached to Tyler Two, understanding instinctively that he is mute because he has seen what has happened to his mother. She says about the brutally murdered white woman, "that poor girl."
Later, Lucy and Sarny come upon the aftermath of yet another battle. Medics are taking away the wounded who can be saved, but leave those with gut wounds behind, because they are bound to die. Four young white soldiers are left dying on the ground, and it is Lucy this time who, with compassion and human decency for the men despite their color, asserts to Sarny, "We'll stay." Lucy and Sarny stay with the men for two days, doing what little they can to ease their dying.