Get labels, ticks, values, and colors for the variable.

def labels_ticks_and_vals(self):
        """Get labels, ticks, values, and colors for the variable."""
        y_ticks = defaultdict(list)
        for y, label, _, vals, color in self.iterator():
            y_ticks[label].append((y, vals, color))
        labels, ticks, vals, colors = [], [], [], []
        for label, data in y_ticks.items():
            labels.append(label)
            ticks.append(np.mean([j[0] for j in data]))
            vals.append(np.vstack([j[1] for j in data]))
            colors.append(data[0][2])  # the colors are all the same
        return labels, ticks, vals, colors