You have imported Tkinter as tk but you are trying to call the Label method directly.
Either call Label from tk.
import Tkinter as tk
root = tk.Tk()
tk.Label(root, text="Red Sun", bg="red", fg="white").pack()
tk.Label(root, text="Green Grass", bg="green", fg="black").pack()
tk.Label(root, text="Blue Sky", bg="blue", fg="white").pack()
or
Don’t import Tkinter as any other name, just use
from Tkinter import *