Change button Color in Kivy

def build(self): 
        # use a (r, g, b, a) tuple 
        btn = Button(text ="Push Me !", 
        font_size ="20sp", 

                # Here you can give the color
                # The value must be between 0 to 1 
                # greyish black color
                background_color =(1, 1, 1, 1),  

                size =(32, 32), 
                size_hint =(.2, .2), 
                pos =(300, 250)) 

        return btn 

## Sample Python application demonstrating the 
## How to change button color in Kivy.
################################################### 
 
# import kivy module 
import kivy 

# to choose the colors randomly 
# every time you run it shows different color 
import random 

# this restricts the kivy version i.e 
# below this kivy version you cannot 
# use the app or software 
kivy.require("1.9.1") 
    
# base Class of your App inherits from the App class. 
# app:always refers to the instance of your application 
from kivy.app import App 
    
# creates the button in kivy 
# if not imported shows the error 
from kivy.uix.button import Button 

# BoxLayout arranges children in a vertical or horizontal box. 
# or help to put the children at the desired location. 
from kivy.uix.boxlayout import BoxLayout 

# declaring the colours you can use directly also 
red = [1, 0, 0, 1] 
green = [0, 1, 0, 1] 
blue = [0, 0, 1, 1] 
purple = [1, 0, 1, 1] 
    
# class in which we are creating the button 
class ChangeColorApp(App): 
        
    def build(self): 
        superBox = BoxLayout(orientation ='vertical') 

        HB = BoxLayout(orientation ='horizontal') 

        # creating the list of defined colors
        colors = [red, green, blue, purple] 
        

        # Changing the color of buttons
        # here you can see how you can change the color
        btn1 = Button(text ="One",
                    # Color of button is changed not default
                    background_color = random.choice(colors), 
                    font_size = 32, 
                    size_hint =(0.7, 1)) 

        btn2 = Button(text ="Two", 
                    background_color = random.choice(colors), 
                    font_size = 32, 
                    size_hint =(0.7, 1)) 

        HB.add_widget(btn1) 
        HB.add_widget(btn2) 

 
        VB = BoxLayout(orientation ='vertical') 

        btn3 = Button(text ="Three", 
                    background_color = random.choice(colors), 
                    font_size = 32, 
                    size_hint =(1, 10)) 

        btn4 = Button(text ="Four", 
                    background_color = random.choice(colors), 
                    font_size = 32, 
                    size_hint =(1, 15)) 

        
        VB.add_widget(btn3) 
        VB.add_widget(btn4) 

        superBox.add_widget(HB) 
        superBox.add_widget(VB) 

        return superBox 

# creating the object root for App class 
root = ChangeColorApp() 
    
# run function runs the whole program 
# i.e run() method which calls the 
# target function passed to the constructor. 
root.run()