Tkinter's checkbutton makes checkmark invisible after changing background color

I am using tkinter to create a simple GUI with python. I wanted to change the background and foreground color of a Checkbutton and while that works, it makes the checkmark itself invisible. It still works, tested with a simple function, but I seem to miss something. Here is the code:

import tkinter as tk

def check1Clicked():
    if var1.get():
        print("clicked")
    else:
        print("not clicked")


root = tk.Tk()
root.geometry("100x100")

var1 = tk.IntVar()
c1   = tk.Checkbutton(root, text="bla", variable=var1,
         onvalue=1, offvalue=0,
         bg="red",fg="white",
         command=check1Clicked
         )
# use "place" to easily center widget
c1.place(relx=.5, rely=.5, anchor="c")

root.mainloop()

Any suggestions what I am missing would be greatly appreciated!

The versions I am using:

python:  3.8.10
tkinter: 8.6

>Solution :

The problem appears to be caused by fg='white', because the check mark matches the foreground color. Ergo, when the box is checked, the checkmark is white on a white background.

To alleviate this, you can either

• Change to fg=black (or omit it entirely since black is the default), but this has the effect of making your text black as well

or

• Change the background color of the checkbox itself with selectcolor=black, so the checkmark will appear as white on a black background (you could really use any color here, just know that the box will use the selectcolor and the check mark will use the fg color)

Neither of these is a perfect solution, unfortunately, but they will work.