TTK Combobox does not style properly

Question

I have been attempting to create a combobox that fits in with the rest of my UI; however the widget still looks like the default:

In my attempts, I have tried to "brute-force" the widget into adapting to the color with the following code but to no avail:

self.root = tk.Tk() # Parent Container

# Other UI elements declared

self.themeSel_combo_theme.configure(
    "TCombobox",
    background=self.theme.get('bg'),
    foreground=self.theme.get('bg'),
    fieldbackground=self.theme.get('bg'),
    darkcolor=self.theme.get('bg'),
    lightcolor=self.theme.get('bg'),
    selectbackground=self.theme.get('bg'),
    selectforeground=self.theme.get('bg'),
    bordercolor=self.theme.get('bg'),
    insertcolor=self.theme.get('bg'),
    insertwidth=self.theme.get('bg'), # It uses a color, not a size value
    arrowcolor=self.theme.get('bg')
)

self.themeSel_combo = ttk.Combobox(self.quickTheme_cont, style="TCombobox")

The code above was made using this website as a reference.

Note that self.theme.get('bg') returns #202020

Answer 1

Apologies for the inconvenience; I've decided to keep this thread in case someone else needs help with this. It turns out that using the following command for creating the parent container makes it so that ttk objects do not style properly:

self.root = tk.Tk()

Changing the aforementioned command to the following fixed the issue I was having:

self.root = tk.Toplevel()