ttk creating and using a custom theme

I was making this far too difficult.

Here was the solution for anybody else trying to figure this out:

from tkinter import *from tkinter import ttkclass Main:    def __init__(self, master):        self.master = master        self.main_button = ttk.Button(self.master, text = 'New', command = self.new_window)        self.main_button.grid()    def new_window(self):        pop_up = Top(self.master)class Top:    def __init__(self, master):        pop_up = self.pop_up = Toplevel(master)        self.pop_up_frame = ttk.Frame(pop_up, height = 100, width = 100)        self.pop_up_frame.grid(sticky = E+W+S+N)        self.s = ttk.Style()        self.s.theme_create('shadow', parent = 'default')        print(self.s.theme_names())        self.c1_button = ttk.Button(pop_up, text = 'Default', command = self.get_default)        self.c2_button = ttk.Button(pop_up, text = 'Vista', command = self.get_shadow)        self.c1_button.grid()        self.c2_button.grid()    def get_default(self):        self.s.theme_use('default')    def get_shadow(self):        self.s.theme_use('vista')        self.s.configure('TButton', foreground = 'white', background = 'blue')        self.s.configure('TFrame', background = 'black')root = Tk()app = Main(root)root.mainloop()

To simplify Gregory6106's answer, you can modify your current theme theme using .configure().

from tkinter import *from tkinter import ttkclass MainPage(ttk.Frame):    def __init__(self, master):        ttk.Frame.__init__(self, master)        self.main_label = ttk.Label(self, text="Pointless Text")        self.main_button = ttk.Button(self, text="Pointless Button")        self.main_label.pack(padx=5, pady=5)        self.main_button.pack(padx=5, pady=5)        # Configure custom theme        self.s = ttk.Style()        self.s.configure('TLabel', foreground='red', background='grey')        self.s.configure('TButton', foreground='white', background='blue')        self.s.configure('TFrame', background='black')root = Tk()app_frame = MainPage(root)app_frame.pack()root.mainloop()

Note: This solution works by configuring the pre-existing, theme rather than creating a new one. As a result, this may not work if you plan on swapping back to the original theme during runtime.