tkinter中函数调用未定义的类

import tkinter as tk
from tkinter import ttk
win=tk.Tk()
aLabel = ttk.Label(win,text="A Label")
aLabel.grid(column=0,row=0)

#Button Click Event Callback Function
#Adding a Button


def clickMe():
    action.configure(text="**I have Clicked!**")
    aLabel.configure(foreground=‘red‘)

action = ttk.Button(win,text="Click Me!",command=clickMe)
action.grid(column=1,row=0)