old_contents: import Image
  import ImageDraw
  import ImageFont
  import screen
  
  class watchout_screen(screen.screen):
  
      def __init__(self):
          screen.screen.__init__(self)
          self.image = Image.open('maximus.jpg')
          self.image = self.image.resize((320,240))
          self.draw_image(self.image , (0,0))
  
          self.bfont = ImageFont.truetype('Montserrat-Regular.ttf', 66)
          self.font = ImageFont.truetype('Montserrat-Regular.ttf', 65)
          self.count = 0
          self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,0,0))
          self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,255,255))
  
      def update(self):
          self.draw_image(self.image , (0,0))
          if self.count == 0 :
              self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,255,255))
              self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,0,0))
          else:
              self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,0,0))
              self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,255,255))
          self.count = 1 - self.count
  
new_contents: import Image
  import ImageDraw
  import ImageFont
  import screen
  
  class watchout_screen(screen.screen):
  
      def __init__(self):
          screen.screen.__init__(self)
          self.image = Image.open('maximus.jpg')
          self.image = self.image.resize((320,240))
          self.draw_image(self.image , (0,0))
  
          self.bfont = ImageFont.truetype('Montserrat-Regular.ttf', 66)
          self.font = ImageFont.truetype('Montserrat-Regular.ttf', 65)
          self.count = 0
          self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,0,0))
          self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,255,255))
  
      def update(self):
          self.draw_image(self.image , (0,0))
          if self.count == 0 :
              self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,255,255))
              self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,0,0))
          else:
              self.draw_text('Watchout!!', (0, 100), self.bfont, fill=(255,0,0))
              self.draw_text('Watchout!!', (0, 100), self.font, fill=(255,255,255))
          self.count = 1 - self.count
          screen.screen.update(self)
  
subject: Add the back buffer blit in the update function