Why does ttk.style() / .configure not apply a defined style to a frame? (python3, tkinter, ttk)

Question

I am trying to write code for a very simple frame layout in tkinter/ tkk to understand how it works and I am running into a problem, where I can't find awnsers online. I am trying to color a frame using the style configure method. I am able to create a new 'TFrame' style object. However, when I set the defined style for a frame it is not applied (see image). The code doesn't through any errors, it just doesn't apply the style. What am I doing wrong? Is this because of my interpreter? I am using Python 3.10.2

This my code:

import tkinter as tk
from tkinter import ttk
root = tk.Tk()
root.title('style Test')
root.geometry('400x300')
style = ttk.Style()
style.configure('new.TFrame', background='green')
style.configure('new.TButton', font=('Myriad Pro', 20), background='red')
mainFrame = ttk.Frame(root, width=200, height=200, style='new.TFrame')
mainFrame.grid()
button = ttk.Button(root, text='Some text' ,style='new.TButton')
button.grid()
root.mainloop()

This my output window:

enter image description here

• acw1668: Style may not be applied to all themes, so try switching to other theme.
• user4136999: @RichardL. Are you running on macos? It worked on Windows 10.
• RichardL: @toyotaSupra I‘m on macOS (13.4.1)
• user4136999: Does this answer your question? Simple Tkinter python Programm doesn't work