Kivymd: change toolbar backgroud color by pressing a button

I'd like to know of there's possible to change Toolbar Background Color by pressing a button. I have 6 buttons with different colors, and when I press it, the toolbar background changes it's colors...

I tried to change creating a method, but returns a error...

def changeThemeColor(self):
        self.root.ids.tbCategorie.md_bg_color = [0, 0, 0, 1]

Here's my code below.

from kivymd.app import MDApp
from kivymd.uix.floatlayout import FloatLayout
from kivy.lang import Builder
from kivymd.uix.button import MDFlatButton
from kivy.uix.scrollview import ScrollView

KV = '''
ScreenManager:
    Screen:
        name: 'screenOption'
        BoxLayout:
            orientation: 'vertical'
            MDToolbar:
                id: tbOption
                md_bg_color: 0, 0, 0, 1
            Options:
                id: screenoption

<Options>
    ScrollView:
        MDList:
            spacing: '20dp'
            padding: '25dp'
            
            MDLabel:    
            BoxLayout:
                MDFlatButton:
                    md_bg_color: (0/255,0/255,0/255)
                    on_release: app.changeThemeColor()
                    line_color: (128/255,128/255,128/255)
                
                MDLabel:        
                MDFlatButton:
                    md_bg_color: (255/255,255/255,255/255)
                    line_color: (128/255,128/255,128/255)
                
                MDLabel:    
                MDFlatButton:
                    md_bg_color: (255/255,0/255,0/255)
                    line_color: (128/255,128/255,128/255)
                
                MDLabel:
                MDFlatButton:
                    md_bg_color: (0/255,0/255,255/255)
                    line_color: (128/255,128/255,128/255)
            
            MDLabel:
            BoxLayout:
                MDFlatButton:
                    md_bg_color: (255/255,0/255,255/255)
                    line_color: (128/255,128/255,128/255)
                
                MDLabel:
                MDFlatButton:
                    md_bg_color: (255/255,255/255,0/255)
                    line_color: (128/255,128/255,128/255)
                
                MDLabel:
                MDFlatButton:
                    md_bg_color: (0/255,128/255,0/255)
                    line_color: (128/255,128/255,128/255)
                    
                MDLabel:
                MDFlatButton:
                    md_bg_color: (128/255,128/255,128/255)
                    line_color: (128/255,128/255,128/255)
'''

class Options(FloatLayout):
    pass
    
class Aplicativo(MDApp):
    
    def changeThemeColor(self):
        self.root.ids.tbCategorie.md_bg_color = [0, 0, 0, 1]
    
    def build(self):
        return Builder.load_string(KV)
        
Aplicativo().run()

By the way, the original code I have at least 5 different toolbar I'd like to change.

Solution

In your posted code tbOption refers to the MDToolbar while tbCategorie has no reference. So in method changeThemeColor you need to change that as,

self.root.ids.tbOption.md_bg_color = [0, 0, 0, 1]

Additionally you might get the following error while setting the md_bg_color,

ValueError: MDToolbar.md_bg_color value length is immutable`

which means that md_bg_color should be a list or tuple (if given in this format other than string, None etc.) of four values between 0 and 1 in [r, g, b, a] format.