Set style for Checkbutton or Labelframe in python tkinter

You need to configure the Label sub-component:

from tkinter import *from tkinter import ttkroot = Tk()s = ttk.Style()s.configure('Red.TLabelframe.Label', font=('courier', 15, 'bold'))s.configure('Red.TLabelframe.Label', foreground ='red')s.configure('Red.TLabelframe.Label', background='blue')lf = ttk.LabelFrame(root, text = "Test", style = "Red.TLabelframe")lf.pack( anchor = "w", ipadx = 10, ipady = 5, padx = 10,                  pady = 0, side = "top")Frame(lf, width=100, height=100, bg='black').pack()print(s.lookup('Red.TLabelframe.Label', 'font'))root.mainloop()

As the accepted answer didn't really help me when I wanted to do a simple changing of weight of a ttk.LabelFrame font (if you do it like recommended, you end up with a misplaced label), I'll provide what worked for me.

You have to use labelwidget option argument of ttk.LabelFrame first preparing a seperate ttk.Label that you style earlier accordingly. Important: using labelwidget means you don't use the usual text option argument for your ttk.LabelFrame (just do it in the label).

# changing a labelframe font's weight to boldroot = Tk()style = ttk.Style()style.configure("Bold.TLabel", font=("TkDefaultFont", 9, "bold"))label = ttk.Label(text="Foo", style="Bold.TLabel")lf = ttk.LabelFrame(root, labelwidget=label)

For completeness sake, I was looking how to change border color style (specifically color) of ttk.LabelFrame and finally found how it worked so wanted to post on the posts that I came across while searching.

I create global styles for my ttk widgets, there are ways to apply this to single widgets as well.

style = ttk.Style()style.theme_create('style', parent='alt',                         settings = {'TLabelframe': {'configure':                                         {'background': 'black',                                        'relief': 'solid', # has to be 'solid' to color                                         'bordercolor': 'orange',                                        'borderwidth': 1}},                                    'TLabelframe.Label': {'configure':                                         {'foreground': 'green',                                        'background': 'black'}}})style.theme_use('style')