#  alternating push button colour
from guizero import App, PushButton

def flash_button():
    if warning_button.bg == "white":
        warning_button.bg = "black"
        app.text_color = "white"
    else:
        warning_button.bg = "white"
        warning_button.text_color = "black"

app = App("Flash Button", bg="white")

# create an warning button
warning_button = PushButton(app, text="WARNING")
warning_button.repeat(1000, flash_button)