Обмен цвета в RedBlack Tree

Question

Я не могу поменять цвет между двумя узлами (Parent_Node и Grand_Parent_Node).

Вставка правильная, некорректна только раскраска узлов. На самом деле, все дерево не получает цвет, кроме корневого узла. RedBlack Tree Java-реализация. Взято из GeeksForGeeks и конвертировано из C++ в Java.

public class RB {
    Node root;
    enum Color {RED, BLACK;}

    public class Node {
        int data;
        Color color;
        Node left, right, parent;

        // Constructor 
        Node(int data) {
            this.data = data;
            left = right = parent = null;
        }
    }

    // This function fixes violations caused by BST insertion 
    void fixViolation(Node root, Node pt) {
        Node parent_pt = null;
        Node grand_parent_pt = null;

        while ((pt != root) && (pt.color != Color.BLACK) && (pt.parent.color == Color.RED)) {
            parent_pt = pt.parent;
            grand_parent_pt = pt.parent.parent;

            /*  Case : A 
                Parent of pt is left child of Grand-parent of pt */
            if (parent_pt == grand_parent_pt.left) {

                Node uncle_pt = grand_parent_pt.right;

                /* Case : 1 
                   The uncle of pt is also red 
                   Only Recoloring required */
                if (uncle_pt != null && uncle_pt.color == Color.RED) {
                    grand_parent_pt.color = Color.RED;
                    parent_pt.color = Color.BLACK;
                    uncle_pt.color = Color.BLACK;
                    pt = grand_parent_pt;
                } else {
                    /* Case : 2 
                       pt is right child of its parent 
                       Left-rotation required */
                    if (pt == parent_pt.right) {
                        rotateLeft(root, parent_pt);
                        pt = parent_pt;
                        parent_pt = pt.parent;
                    }

                    /* Case : 3 
                       pt is left child of its parent 
                       Right-rotation required */
                    rotateRight(root, grand_parent_pt);
                    swap(parent_pt.color, grand_parent_pt.color);
                    pt = parent_pt;
                }
            }

            /* Case : B 
               Parent of pt is right child of Grand-parent of pt */
            else {
                Node uncle_pt = grand_parent_pt.left;

                /*  Case : 1 
                    The uncle of pt is also red 
                    Only Recoloring required */
                if ((uncle_pt != null) && (uncle_pt.color == Color.RED)) {
                    grand_parent_pt.color = Color.RED;
                    parent_pt.color = Color.BLACK;
                    uncle_pt.color = Color.BLACK;
                    pt = grand_parent_pt;
                } else {
                    /* Case : 2 
                       pt is left child of its parent 
                       Right-rotation required */
                    if (pt == parent_pt.left) {
                        rotateRight(root, parent_pt);
                        pt = parent_pt;
                        parent_pt = pt.parent;
                    }

                    /* Case : 3 
                       pt is right child of its parent 
                       Left-rotation required */
                    rotateLeft(root, grand_parent_pt);
                    swap(parent_pt.color, grand_parent_pt.color);
                    pt = parent_pt;
                }
            }
        }

        root.color = Color.BLACK;
    }

    void swap(Color color, Color color2) {
        // TODO Auto-generated method stub
        Color temp;
        temp = color;
        color = color2;
        color2 = temp;
    }
}

исключая основную функцию и функцию вставки BST.