我编写了python tkinter按钮来获得颜色，但它们没有

Question

在程序中，我指定按钮的文本有颜色，但它们显示为黑色，我从未收到错误消息。

这是我的代码：

from Tkinter import *

root = Tk()

topFrame = Frame(root)
topFrame.pack()
bottomFrame = Frame(root)
bottomFrame.pack(side = BOTTOM)

button1 = Button(topFrame,text = "Button 1",fg = "red")
button2 = Button(topFrame,text = "Button 2",fg = "green")
button3 = Button(topFrame,text = "Button 3",fg = "blue")
button4 = Button(bottomFrame,text = "Button 4",fg = "purple")

button1.pack(side = LEFT)
button2.pack(side = LEFT)
button3.pack(side = LEFT)
button4.pack(side = BOTTOM)

root.mainloop()