import tkinter as tk
from random import randint

lst = ["red", "green", "blue", "yellow", "grey"]
indice_couleur = randint(0, len(lst))
taille = randint(10, 31)
position_x = randint(0, 401)
position_y = randint(0, 301)

fenetre = tk.Tk()

canva = tk.Canvas(fenetre, width = 400, height = 300, bg = "white")
canva.grid()

rectangle = tk.Rectangle(fenetre, position_x, position_y, position_x+taille, position_y+taille)

fenetre.mainloop()