[Tkinter] changing background color of a button

[ieee488]

I am a beginner to Python but not to programming in general.

I have the following code for creating 3 buttons:

for i in range(1, 3):
    aButton = "button" + str(i)
    aButton = tkinter.Button(Gui, font=Font1, text=i, image=myPixel, width=70, height=70, compound="c", bg='white', activebackground='white')
    aButton['command'] = partial(setBG, aButton)
    aButton.grid(row=1, column=i)

And it works. I get a three buttons.

Now, I want to use a function called ChangeColor to change the background color to red.

def ChangeColor():
    tkinter.button1['bg'] = 'red'

I run the script but I get

Error:
module 'tkinter' has no attribute 'button1'

How do I get a reference to any of the three buttons and change its background color?

.