How to set the background color of a ttk.Combobox

Apparently, the order you set the properties of the new style is important to determine if a certain property of the new style will be applied or not. For example, if I set first the background instead of selectbackground, then the color of selection will not be changed, but just the mini button color with the arrow (to list down the options).

I noted also that depending on the value of parent, which I suppose is the parent style from which the new style is derived, some of the new settings and properties of the new style might not be applied. For example, if I try to change the fieldbackground property when parent is set to aqua, it does not work, but if parent is set to alt, it works. (I hope more expert users can help and contribute to improve this answer, which could be helpful also for future users of ttk and tkinter).

This is my solution, where I created a complete new style:

import tkinter as tkfrom tkinter import ttkroot = tk.Tk()combostyle = ttk.Style()combostyle.theme_create('combostyle', parent='alt',                         settings = {'TCombobox':                                     {'configure':                                      {'selectbackground': 'blue',                                       'fieldbackground': 'red',                                       'background': 'green'                                       }}}                         )# ATTENTION: this applies the new style 'combostyle' to all ttk.Comboboxcombostyle.theme_use('combostyle') # show the current styles# print(combostyle.theme_names())combo = ttk.Combobox(root, values=['1', '2', '3'])combo['state'] = 'readonly'combo.pack()entry = tk.Entry(root)entry.pack()root.mainloop()

Since I am not an expert on ttk, I was not able to apply a new theme just to a certain instance of type ttk.Combobox, but I applied the theme to all instances of future possible ttk.Combobox. If someone can improve this answer, I would really appreciate the gesture!

For more information on how to create and set new styles, see here or here.

This code below worked fine for me.It is important set the order of the parameters.

style = ttk.Style()style.map('TCombobox', fieldbackground=[('readonly','white')])style.map('TCombobox', selectbackground=[('readonly', 'white')])style.map('TCombobox', selectforeground=[('readonly', 'black')])self.mycombo = ttk.Combobox(self.frame,textvariable=self.combo_var,                            height=15,justify='left',width=21,                            values=lista)self.mycombo['state'] = 'readonly' # Set the state according to configure colorsself.mycombo.bind('<<ComboboxSelected>>',                  lambda event: self._click_combo())

If you just want to change the color without regard to the state of the widget (ie. hover, pressed, etc...), then you will want to use the configure method instead of the map method, as the map method is meant specifically for applying various formats to specific widget states. Since you are only using the "readonly" state, I assume this is what you want.

style.configure('TCombobox', fieldbackground='red')