如何设置tk.simpledialog的背景色？

import tkinter as tk
from tkinter import simpledialog

class CustomDialog(simpledialog.Dialog):
    def body(self, master):
        tk.Frame.__init__(self, master)
        self.configure(bg='lightblue')  # 设置背景色为 lightblue
        tk.Label(self, text="这是一个自定义对话框", bg='lightblue').pack(padx=5, pady=5)
        self.entry = tk.Entry(self)
        self.entry.pack(padx=5, pady=5)
        return self.entry  # initial focus

    def apply(self):
        self.result = self.entry.get()

root = tk.Tk()
root.withdraw()  # Hide the root window

dialog = CustomDialog(root)
print("输入的内容是:", dialog.result)

root.destroy()