from tkinter import *

BLUE  = 1
RED   = 2
GREEN = 3

def bg1():
    root.configure(background="blue".format(clicks))

def bg2():
    root.configure(background="red".format(clicks))

def bg3():
    root.configure(background="green".format(clicks))

def Clicker():
    global clicks
    global flag
    clicks += 1
    root.title("Clicks {}".format(clicks))

if color == BLUE:
    bg1()
    color = RED

elif color == RED:
   bg2()
   color = GREEN

elif color == GREEN:
   bg3()
   color = BLUE

else:
   pass

clicks = 0
color  = BLUE
root = Tk()
root.geometry("400x200")
root.configure()
but = Button(width=30, command=Clicker)
but.pack()
root.mainloop()