from tkinter import *
import random
tk = Tk()
canvas = Canvas(tk, width=400,height=400)
canvas.pack()

def random_rectangle(width, height, fill_color):
    x1 = random.randrange(width)
    y1 = random.randrange(height)
    x2 = random.randrange(x1 + random.randrange(width))
    y2 = random.randrange(y1 + random.randrange(height))
    canvas.create_rectangle(x1, y1, x2, y2, fill=fill_color)

random_rectangle(400, 400, 'green')
random_rectangle(400, 400, 'red')
random_rectangle(400, 400, 'blue')
random_rectangle(400, 400, 'orange')
random_rectangle(400, 400, 'yellow')
random_rectangle(400, 400, 'pink')
random_rectangle(400, 400, 'purple')
random_rectangle(400, 400, 'violet')
random_rectangle(400, 400, 'magenta')
random_rectangle(400, 400, 'cyan')
random_rectangle(400, 400, '#ffd800')