flip_blackorWhite

from guizero import App, PushButton


def flip_color():
    if app.bg == "white":
       app.bg = "black"
    else :
       app.bg = "white"

def stop_flip():
    app.destroy()

app = App("Flip Colour", bg="white")

btn_start = PushButton(app, command=flip_color, text='Recolorize')
btn_stop = PushButton(app, command=stop_flip, text='Stop It')

app.repeat(5000, flip_color)

app.display()