How to see more than one change in same function when using sleep in Python PySide2

Question

I am trying to execute more than one action in same function. In the code below you are going to see a window page with a button and a label. I want to see "BLUE" and after 2 second of sleep I want to see "RED" text on my label. But when I click the button all function work like a block and after two second of slepp the label text changing to "RED". Yes first it change to BLUE but I can not see that because its too fast. How can I fix that?

class Form(QDialog):

def __init__(self, parent=None):
    super(Form, self).__init__(parent)
    #label is Hello now
    self.label=QLabel("Hello")
    self.button = QPushButton("Change it")
    layout = QVBoxLayout()
    layout.addWidget(self.label)
    layout.addWidget(self.button)
    self.setLayout(layout)
    self.button.clicked.connect(self.func)
def func(self):
    self.label.setText("BLUE")
    time.sleep(2)
    self.label.setText("RED")

Answer 1

void QTimer::singleShot(int msec, const QObject *receiver, const char *member)

This static function calls a slot after a given time interval.

from PyQt5.QtCore    import *
from PyQt5.QtGui     import *
from PyQt5.QtWidgets import *

class Form(QDialog):

    def __init__(self, parent=None):
        super(Form, self).__init__(parent)
        
        #label is Hello now
        self.label  = QLabel("Hello")
        self.button = QPushButton("Change it")
        self.button.clicked.connect(self.func)
        
        layout = QVBoxLayout()
        layout.addWidget(self.label)
        layout.addWidget(self.button)
        self.setLayout(layout)
        
    def func(self):
        self.label.setText("BLUE")
#        QApplication.processEvents()      
#        QThread.msleep(2000)              
#        self.label.setText("RED")
        QTimer.singleShot(2000, lambda : self.label.setText("RED"))       # <----
    
if __name__ == "__main__":
    import sys
    app = QApplication(sys.argv)
    w = Form()
    w.show()
    sys.exit(app.exec_())