Qt for Python (PySide/Shiboken)

Hey everyone, I'm starting to use QT Designer and PySide6, and I have a question. In the code below, the button color and the button text color are not applied. No errors occur, but the color remains the same. What could be missing? Please help me. import sys from PySide6.QtWidgets import QMainWindow, QApplication, QStyleFactory from MainWindow_Dark_Light import Ui_MainWindow import styles class MainWindow(QMainWindow, Ui_MainWindow): def init(self): super(MainWindow, self).init() self.setupUi(self) self.btn_Dark.clicked.connect(self.set_dark) self.btn_Light.clicked.connect(self.set_light) def set_dark(self): app = QApplication.instance() styles.dark(app) def set_light(self): app = QApplication.instance() styles.light(app) app = QApplication() # Definir o estilo "Fusion" app.setStyle(QStyleFactory.create('Fusion')) w = MainWindow() w.show() # styles.dark(app) app.exec() ———————————————————————————- from PySide6.QtGui import QPalette, QColor, QBrush from PySide6.QtCore import Qt def dark(app): darkPalette = QPalette() # darkPalette = QBrush() darkPalette.setColor(QPalette.Window, QColor(53, 53, 53)) darkPalette.setColor(QPalette.WindowText, QColor(121, 121, 121)) darkPalette.setColor(QPalette.Button, QColor(0, 0, 0)) darkPalette.setColor(QPalette.ButtonText, QColor(255, 255, 255)) app.setPalette(darkPalette) def light(app): lightPalette = QPalette() lightPalette.setColor(QPalette.Window, QColor(255, 255, 255)) lightPalette.setColor(QPalette.WindowText, QColor(0, 0, 0)) lightPalette.setColor(QPalette.Button, QColor(255, 255, 255)) lightPalette.setColor(QPalette.ButtonText, QColor(0, 0, 0)) app.setPalette(lightPalette)