from tkinter import *
COLOR = "black"
root = Tk()
root.config(bg=COLOR)
button = Button(text="button", bg=COLOR)
button.pack(padx=5, pady=5)
entry = Entry(bg=COLOR, fg='white')
entry.pack(padx=5, pady=5)
text = Text(bg=COLOR, fg='white')
text.pack(padx=5, pady=5)
root.mainloop()