I'm writing a slideshow program with Tkinter, but I don't know how to change the background color to black instead of the standard light gray. How can this be done?

import os, sys
import Tkinter
import Image, ImageTk
import time

root = Tkinter.Tk()
w, h = root.winfo_screenwidth(), root.winfo_screenheight()
root.overrideredirect(1)
root.geometry("%dx%d+0+0" % (w, h))
root.focus_set()
root.bind("<Escape>", lambda e: e.widget.quit())
image = Image.open(image_path+f)
tkpi = ImageTk.PhotoImage(image)        
label_image = Tkinter.Label(root, image=tkpi)
label_image.place(x=0,y=0,width=w,height=h)
root.mainloop(0)