import tkinter as tk

def Call():
    msg = tk.Label(window, text="Presionaste el botón")
    msg.place(x=30, y=50)
    button["bg"] = "blue"
    button["fg"] = "white"

window = tk.Tk()
window.geometry("200x100")
button = tk.Button(text="Presioname", command=Call)
button.place(x=30, y=20, width=120, height=25)
window.mainloop()