from guizero import App, Box, PushButton, Text, TextBox
app = App(height=300)

def click_button3():
    box3.bg="green"


box1 = Box(app, align="top", width="fill", height=100, border=0)
box1.bg="green"
lbl1 = Text(box1, text="It is text of Green box!")


box2 = Box(app, align="none", width="fill", height=100, border=0)
box2.bg="red"
textbox = TextBox (box2)
textbox.bg="white"
textbox.color="balck"

box3 = Box(app, align="none", width="fill", height=100, border=0)
box3.bg="blue"
button3 = PushButton(box3, text="Done", command=click_button3)

app.display()# Write your code here :-)