from Tkinter import *
import ttk
import tkMessageBox

root = Tk()
root.title("Colour!")

canvasColor = "yellow"

def buttonRed() :
    canvas = Canvas(root, bg = "red", height=100, width=100)
    canvas.grid(row=0,column=2)

button = ttk.Button(root, text="Red", command = buttonRed)
button.grid(row=2,column=1)

button2 = ttk.Button(root, text ="Green", command = buttonGreen)
button2.grid(row=2,column=2)

button3 = ttk.Button(root, text="Blue", command = buttonBlue)
button3.grid(row=2,column=3)

canvas = Canvas(root, bg = canvasColor, height=200, width=200)
canvas.grid(row=0,column=2)


root.configure(background='white')
root.mainloop()