问如何改变随机.选择python？

EN

my_list = ["red" , "blue" , "green" , "yellow"]

from tkinter import *
import random
win = Tk()

def change_label_1():
    colours = ['red' , 'green' , 'gray' , 'black' , 'purple' , 'orange']
    selection1 = random.choice(colours)
    selection2 = random.choice(colours)
    label_1['bg']= selection1
    label_1['fg']= selection2


label_1 = Label(win ,
            bd= 8,
            relief= "solid",
            font= "times 22 bold",
            bg= "red",
            fg= "white",
            text= "Hello World")

label_1.pack()

btn_1 = Button(win,
           relief= "solid" ,
           font= "Times 22 bold" ,
           bg= "black" ,
           fg= "purple" ,
           text= "Change" ,
           command= change_label_1)
btn_1.pack()


win.mainloop()