As ultramailman mentioned, you initialized "WHITE" but never used it anywhere. The value is correct for a true white color, it just comes down to setting the color of the screen.
and after that you are going to want to make sure that you use pygame's flip method to properly display the screen.
I'm not sure why it isn't in the code sections above but i called for "DISPLAY" to be filled "WHITE" and it is not working. I combined CreateDisplay.py and Game.py, and added pygame.diplsay.flip() to the Game() definition and it works fine now. I assumed having pygame.display.update() in Main.py would be enough.